Bloomer concealed by cagey ex-officer on the way up (5)
I believe the answer is:
oxeye
'bloomer' is the definition.
(oxeye is a kind of flowering plant)
'concealed by cagey ex-officer on the way up' is the wordplay.
'concealed by' indicates a hidden word.
'on the way up' is a reversal indicator.
'eyexo' is hidden in the letters of 'cagey ex officer'.
'eyexo' in reverse letter order is 'OXEYE'.
(Other definitions for oxeye that I've seen before include "Type of daisy" , "Flower; _ daisy" , "A daisy, the marguerite" , "Daisy-like flower" , "Wild daisy" .)