Fret (5)
'fret' is the definition.
(I know that fret is a more specific form of the action the worry)
This is all the clue.
(Other definitions for worry that I've seen before include "Fret, be disturbed in mind" , "(Feel) anxiety" , "Concern, anxiety, uneasiness" , "Bother" , "'Anxiety, uneasiness (5)'" .)
'fret' is the definition.
(I know that fret can be written as stew)
This is all the clue.
(Other definitions for stew that I've seen before include "Ragout or burgoo" , "Tight spot" , "Meat and veg dish" , "Agitation; food" , "are nervous" .)
'fret' is the definition.
(both can mean to worry or dread)
This is the entire clue.
(Other definitions for agonise that I've seen before include "rack" , "Torment oneself" , "Be in torments of indecision" , "Struggle mentally" , "Suffer extreme mental pain" .)