Recruits unusually silent before start of service (7)
I believe the answer is:
enlists
'recruits' is the definition.
(enlisting is a kind of recruiting)
'unusually silent before start of service' is the wordplay.
'unusually' indicates an anagram.
'before' means one lot of letters go next to another.
'start of' suggests taking the first letters.
The first letter of 'service' is 's'.
'silent' with letters rearranged gives 'enlist'.
'enlist'+'s'='ENLISTS'
(Other definitions for enlists that I've seen before include "Signs up" , "Joins up" , "Registers" , "volunteers" , "Recruits" .)