Kind of word sent round in brief note (4)
I believe the answer is:
verb
'kind of word' is the definition.
(verb is a type of word)
'sent round in brief note' is the wordplay.
'sent round in' is a reversal indicator.
'brief' means to remove the last letter (a shorter or briefer version of the word).
'note' becomes 'breve' (musical note).
'breve' with its final letter taken away is 'brev'.
'brev' in reverse letter order is 'VERB'.
(Other definitions for verb that I've seen before include "Maybe protest" , "Old-fashioned art, for example" , "Word that denotes an action or a state" , "A word that conveys action" , "Predicate of a sentance (4)" .)