Sucks up (7)
I believe the answer is:
absorbs
'sucks up' is the definition.
('absorb' can be a synonym of 'suck up')
This is all the clue.
(Other definitions for absorbs that I've seen before include "Swallows up" , "Occupies the mind" , "Takes in, sucks up" , "Engrosses" , "Soaks up" .)