Catch some veterans nervously retreating (7)
I believe the answer is:
ensnare
'catch' is the definition.
(I know that ensnare is a kind of catch)
'some veterans nervously retreating' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'retreating' says the letters should be written in reverse.
'eransne' is hidden within 'veterans nervously'.
'eransne' backwards is 'ENSNARE'.
(Other definitions for ensnare that I've seen before include "Capture, trap" , "Ambush" , "Ecstatic expression of feeling" , "Catch as if in a trap or net" .)