Military group you join together, we hear (4)
I believe the answer is:
unit
'military group' is the definition.
(I've seen this before)
'you join together we hear' is the wordplay.
'you' becomes 'u' (I've seen this in other clues).
'join together' becomes 'knit' (I've seen this before).
'we hear' indicates a 'sounds like' (homophone) clue.
'knit' sounds like 'nit'.
'u'+'nit'='UNIT'
(Other definitions for unit that I've seen before include "Entity, system; component group" , "squad" , "Military team" , "Subdivision of a whole" , "Subdivision of a military group" .)