Chap requiring some oxygen, temporarily (4)
I believe the answer is:
gent
'chap' is the definition.
(both can mean a man)
'some oxygen temporarily' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'GENT' is hidden in the letters of 'oxygen temporarily'.
'requiring' is the link.
(Other definitions for gent that I've seen before include "Refined man (colloquial)" , "Informal and short man" , "Honourable man" , "Chap, fellow" , "Toff" .)