Recruit, strangely silent (6)
I believe the answer is:
enlist
'recruit' is the definition.
(enlisting is a kind of recruiting)
'strangely silent' is the wordplay.
'strangely' indicates an anagram.
'silent' with letters rearranged gives 'ENLIST'.
(Other definitions for enlist that I've seen before include "Join up in silent way" , "Obtain help of" , "Listen (anag.)" , "Enrol - recruit" , "Register" .)