Man sees crackers all together (2,5)
I believe the answer is:
en masse
'all together' is the definition.
(I've seen this in another clue)
'man sees crackers' is the wordplay.
'crackers' indicates anagramming the letters (informal term for mad).
'man'+'sees'='mansees'
'mansees' with letters rearranged gives 'EN MASSE'.
(Other definitions for en masse that I've seen before include "All together - in France (2.5)" , "in concert" , "as a bunch" , "All together as a group" , "Many as one" .)