Sailor boy not yet up and about (4)
I believe the answer is:
abed
'not yet up and about' is the definition.
(I've seen this before)
'sailor boy' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'boy' becomes 'ed' (**).
'ab'+'ed'='ABED'
(Other definitions for abed that I've seen before include "how we all hope to go?" , "in his hammock awaiting Santa?" , "having a lie-in?" , "Sleeping (archaic)" , "Tucked up for the night" .)