Deplorable grids in sets to be reworked (11)
I believe the answer is:
distressing
'deplorable' is the definition.
(thesaurus)
'grids in sets to be reworked' is the wordplay.
'to be reworked' indicates anagramming the letters.
'grids'+'in'+'sets'='gridsinsets'
'gridsinsets' anagrammed gives 'DISTRESSING'.
(Other definitions for distressing that I've seen before include "Causing great anxiety" , "Very upsetting" .)