Something to chew sucker brought up (3)
I believe the answer is:
gum
'something to chew' is the definition.
(I've seen this in another clue)
'sucker brought up' is the wordplay.
'sucker' becomes 'mug' (synonyms).
'brought up' says the letters should be written backwards (in a down clue, letters go up).
'mug' backwards is 'GUM'.
(Other definitions for gum that I've seen before include "Sticky stuff - tree" , "seal" , "Eg, a eucalyptus" , "Part of mouth; a tree" , "surrounding roots of teeth?" .)