Part of speech from bishop backing retired vicar, perhaps (4)
I believe the answer is:
verb
'part of speech' is the definition.
(verb is a kind of part of speech)
'bishop backing retired vicar perhaps' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'backing' is a charade indicator (letters next to each other).
'retired' is a reversal indicator.
'vicar perhaps' becomes 'rev' (short for reverend).
'rev' reversed gives 'ver'.
'b' put after 'ver' is 'VERB'.
'from' is the link.
(Other definitions for verb that I've seen before include "Type of word indicating action" , "The predicate of a sentence" , "love, for example" , "Old-fashioned art, for example" , "Word such as run, make, or do" .)