Continental gent to engage troops (6)
I believe the answer is:
signor
'continental gent' is the definition.
(Italian equivalent of 'mister')
'engage troops' is the wordplay.
'engage' becomes 'sign' (signing is a kind of engaging).
'troops' becomes 'or' (military abbreviation for other ranks).
'sign'+'or'='SIGNOR'
'to' is the link.
(Other definitions for signor that I've seen before include "Italian gentleman" , "Italian mister" , "Title of Italian man" , "Title of Italian-speaking man" , "Guy in Rome" .)