Female carries oxygen pump, perhaps (4)
I believe the answer is:
shoe
'pump perhaps' is the definition.
(pump is a kind of shoe)
'female carries oxygen' is the wordplay.
'female' becomes 'she' (I've seen this before).
'carries' is an insertion indicator.
'oxygen' becomes 'o' (atomic symbol for oxygen).
'she' going around 'o' is 'SHOE'.
(Other definitions for shoe that I've seen before include "One of the things racehorse needs" , "Brogue, for example" , "Sandal, for instance" , "From which playing cards are dealt one at a time" , "Flash socket on camera" .)