Give up part of the attic, once development occurs (7)
I believe the answer is:
concede
'give up' is the definition.
(conceding is a kind of giving up)
'part of the attic once development occurs' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'CONCEDE' can be found hidden inside 'attic once development occurs'.
(Other definitions for concede that I've seen before include "Acknowledge - abandon" , "Acknowledge defeat" , "Make concession" , "Allow - give up" , "Make admission" .)