Now in trim for the procession (6)
I believe the answer is:
parade
'the procession' is the definition.
(parade is a kind of procession)
'now in trim' is the wordplay.
'now' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'in' means one lot of letters goes inside another.
'trim' becomes 'pare' (synonyms).
'ad' put inside 'pare' is 'PARADE'.
'for' is the link.
(Other definitions for parade that I've seen before include "Carnival" , "'Procession of bands, floats, etc (6)'" , "March past" , "Promenade" , "Show (put on by soldiers?)" .)