Dress up lie foolishly covering a resentment (11)
I believe the answer is:
displeasure
'resentment' is the definition.
(thesaurus)
'dress up lie foolishly covering a' is the wordplay.
'foolishly' indicates anagramming the letters.
'covering' indicates putting letters inside.
'dress'+'up'+'lie'='dressuplie'
'dressuplie' with letters rearranged gives 'displesure'.
'displesure' going around 'a' is 'DISPLEASURE'.
(Other definitions for displeasure that I've seen before include "Annoyance, disapproval" , "Feeling of annoyance" .)