Ray
You need to provide extra frames for the 1st clip which is equal to the transition timing.
For example if the transition last 2 seconds you need to add 50 frames
for PAL and 60 frames for NTSC format or simply put increase the 1st clip length by 2 seconds PC specs :
OS Windows 10.0 Pro
MB - AS rock Z77 extreme 11
Intel 3770K @ 4.0 Ghz OC
Gskill 32 GB RAM 1800 Mhz
6 TB HDD, SSD bootable
nVidia ASUS GTX 660 Ti
BenQ 22" LCD monitor 1920x1080

A transition's maximum length is determined by the size of the smallest of the two clips, it will be half the length of the smallest clip. If you have a transition set at the default of 2 seconds and you have a 2 second and a 1 minute clip - the transition will eat into half the smallest clip - Just remember this as it will have an effect when you put a transition on either end of a short clip.

Babdi's suggestion should be noted - lengthen the clip to suit OR shorten the duration of the transition.

Dafydd

Dafydd Bevan
I forgot the transition time divided by two part. Thanks for the input.
Ray
Correction to my earlier post.
Increase the time by a second or increase 30 frames ie., 2 second transition divided by 2 = 1 second = 30 frames.
Again if the voice in the clip extends over the video the length of the clip should be corrected till entire voice track is covered by inserting a colour card in the video time line to fill the length of audio track.
Extension of audio track over the length of the video track can happen if the audio track of the clip is seperated from the video clip.
PC specs :
OS Windows 10.0 Pro
MB - AS rock Z77 extreme 11
Intel 3770K @ 4.0 Ghz OC
Gskill 32 GB RAM 1800 Mhz
6 TB HDD, SSD bootable
nVidia ASUS GTX 660 Ti
BenQ 22" LCD monitor 1920x1080