Sleeps around for some period of time (4)
I believe the answer is:
span
'some period of time' is the definition.
(span is a kind of period of time)
'sleeps around' is the wordplay.
'sleeps' becomes 'naps' (napping is a kind of sleeping).
'around' shows that the letters should be reversed in order.
'naps' reversed gives 'SPAN'.
'for' acts as a link.
(Other definitions for span that I've seen before include "too short for the foot" , "Go across" , "Bridge - spick and ___" , "Extent from end to end or across" , "Ox team; bridge" .)