Sees man's form in a body (2,5)
I believe the answer is:
en masse
'in a body' is the definition.
(I've seen this before)
'sees man's form' is the wordplay.
'form' is an anagram indicator.
'sees'+'man'='seesman'
'seesman' is an anagram of 'EN MASSE'.
(Other definitions for en masse that I've seen before include "All together as a group" , "In force" , "As a body (Fr.)" , "All together - in France (2.5)" , "in concert" .)