Joins in midweek? (4)
I believe the answer is:
weds
This clue is a double definition.
'joins' is the first definition.
(I've seen this in another clue)
'midweek?' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for weds that I've seen before include "Marries" , "midweek" , "Makes match" , "Gets married" , "Wagers no longer" .)