Man, that's small for recruits (7)
I believe the answer is:
rookies
'recruits' is the definition.
(I've seen this before)
'man that's small' is the wordplay.
'man' becomes 'rook' (rook is a kind of man).
'that's' becomes 'ie'.
'small' becomes 's' (abbreviation - e.g. clothes size).
'rook'+'ie'+'s'='ROOKIES'
'for' is the link.
(Other definitions for rookies that I've seen before include "Novices in American army" , "trainees" , "Raw beginners" , "Ok, I rose awkwardly with the recruits" , "New recruits as in army" .)