Sailors at ball drink up (6)
I believe the answer is:
absorb
'drink up' is the definition.
(thesaurus)
'sailors at ball' is the wordplay.
'sailors' becomes 'abs' (AB is short for able seaman).
'at' is a charade indicator (letters next to each other).
'ball' becomes 'orb' (both can mean a sphere).
'abs'+'orb'='ABSORB'
(Other definitions for absorb that I've seen before include "Suck up, as a sponge" , "Assimilate or soak up" , "Grip" , "Soak up, as a sponge" , "Take or drink in" .)