Fellow regretted keeping guitar, not getting it (10)
I believe the answer is:
frustrated
'fellow' is the definition.
Both the definition and answer are adjectives. Maybe they are linked in a way I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for frustrated that I've seen before include "Having a sense of discouragement and dissatisfaction" , "Thwarted" , "Disappointingly unsuccessful" , "Prevented from progressing" , "Disheartened" .)