Senior officers kiss cheek (5,4)
I believe the answer is:
brass neck
'cheek' is the definition.
(both can mean insolence or rudeness)
'senior officers kiss' is the wordplay.
'senior officers' becomes 'brass' (the top brass).
'kiss' becomes 'neck' (neck can informally mean to kiss).
'brass'+'neck'='BRASS NECK'
(Other definitions for brass neck that I've seen before include "Effrontery" , "Offering cheek" .)