Retainer dispatched to collect regular bits of trivia (7)
I believe the answer is:
servant
'retainer' is the definition.
('servant' can be a synonym of 'retainer')
'dispatched to collect regular bits of trivia' is the wordplay.
'dispatched' becomes 'sent' (I've seen this before).
'to collect' is an insertion indicator.
'regular bits of' indicates alternate letters.
The alternating letters of 'trivia' are 'rva'.
'sent' placed around 'rva' is 'SERVANT'.
(Other definitions for servant that I've seen before include "House employee" , "Butler, e.g." , "One in domestic service" , "Maid or butler, say" , "Perhaps chauffeur" .)