When I let a wild dove out, it's worth seeing (5)
I believe the answer is:
video
'when i let' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'a wild dove out it's worth seeing' is the wordplay.
'a wild' indicates an anagram.
'out' is an insertion indicator.
'it's worth seeing' becomes 'i' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'dove' with letters rearranged gives 'vdeo'.
'vdeo' enclosing 'i' is 'VIDEO'.
Can you help me to learn more?
(Other definitions for video that I've seen before include "Who killed the radio star? (5)" , "Film recording" , "Taped film" , "Recording medium" , "Visual element of television" .)