Delighted with make-up, but careless (4-5)
I believe the answer is:
slap-happy
'careless' is the definition.
(I've seen this before)
'delighted with make-up' is the wordplay.
'delighted' becomes 'happy' (I've seen this before).
'with' says to put letters next to each other.
'make-up' becomes 'slap' (informal term for make-up).
'happy' put after 'slap' is 'SLAP-HAPPY'.
'but' acts as a link.
(Other definitions for slap-happy that I've seen before include "free with the greasepaint?" , "Boisterously" , "Silly - unmethodical - punch-drunk" , "Cheerfully irresponsible" .)