Maybe keep head office development (5,5)
I believe the answer is:
tower block
'office development' is the definition.
'maybe keep head' is the wordplay.
'maybe keep' becomes 'tower' (keep is a type of castle).
'head' becomes 'block' (a barber's block is a head for storing a wig).
'tower'+'block'='TOWER-BLOCK'
(Other definitions for tower block that I've seen before include "Tall building of offices, flats" , "large building" , "urban building" , "at which 29 [BOLEYN] finished?" , "Skyscraper" .)