Glue to fix mug (3)
I believe the answer is:
gum
'glue' is the definition.
(I know that glue can be written as gum)
'fix mug' is the wordplay.
'fix' indicates anagramming the letters.
'mug' is an anagram of 'GUM'.
'to' acts as a link.
(Other definitions for gum that I've seen before include "A chopper base" , "Adhesive for chewing" , "Part of mouth; a tree" , "Gingeva is its technical name" , "Leaving body" .)