Regret taking the part of Pantagruel (3)
I believe the answer is:
rue
'regret' is the definition.
(I've seen this before)
'the part of pantagruel' is the wordplay.
'the part of' says the answer is hidden in the clue.
'RUE' is hidden within 'pantagruel'.
'taking' is the link.
(Other definitions for rue that I've seen before include "Bitter-tasting herb" , "Deplore" , "Feel sorry" , "At one time, pity" , "Be regretful" .)