identity needed by Man in a manner of speaking (5)
I believe the answer is:
idiom
'in a manner of speaking' is the definition.
(I've seen this before)
'identity needed by man' is the wordplay.
'identity' becomes 'id' (abbreviation).
'needed by' is a charade indicator (letters next to each other).
'man' becomes 'iom' (abbreviation for Isle of Man).
'id'+'iom'='IDIOM'
(Other definitions for idiom that I've seen before include "Distinctive speech" , "Colloquial saying" , "Phrase with a meaning that is not literal" , "'Break a leg' or 'miss the boat'" , "Manner of speaking or writing" .)