Engage in silent wrestling (6)
I believe the answer is:
enlist
'engage' is the definition.
(I know that engage can be written as enlist)
'silent wrestling' is the wordplay.
'wrestling' indicates an anagram.
'silent' anagrammed gives 'ENLIST'.
'in' is the link.
(Other definitions for enlist that I've seen before include "Register" , "Enrol in the services" , "Join up - tinsel (anag)" , "Listen (anag.)" , "Sign on -- 13 (anag)" .)