Chew a piece of gum unchecked (5)
I believe the answer is:
munch
'chew' is the definition.
(I know that munch is a more specific form of the action chew)
'a piece of gum unchecked' is the wordplay.
'a piece of' says the answer is hidden in the clue.
'MUNCH' can be found hidden inside 'gum unchecked'.
(Other definitions for munch that I've seen before include "Chew steadily and vigorously" , "Chomp" , "champ" , "who's popular in the gallery?" , "Eat noisily" .)