Barker, for instance, has 'appeal' (3)
I believe the answer is:
sue
'appeal' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for sue that I've seen before include "Take proceedings against (a person)" , "Litigious girl" , "- - Barker, 19 star" , "Bring a legal action" , "Seek damages" .)