Collapse of penthouse maybe owned by banker (7)
I believe the answer is:
deflate
'collapse' is the definition.
(I know that deflate is a more specific form of the action collapse)
'penthouse maybe owned by banker' is the wordplay.
'penthouse maybe' becomes 'flat' (penthouse is a type of flat).
'owned by' is an insertion indicator.
'banker' becomes 'dee' (I've seen this in other clues).
'flat' inserted inside 'dee' is 'DEFLATE'.
'of' acts as a link.
(Other definitions for deflate that I've seen before include "Release air from" , "Let the wind out of, braggart or balloon" , "Puncture, collapse like balloon" , "Take air" , "Release gas from" .)