Check claim involving northern dispute (9)
I believe the answer is:
Here is my best explanation:
'dispute' is the definition.
('challenge' can be a synonym of 'dispute')
'check claim involving northern' is the subsidiary indication.
'check' becomes 'ch' (I've seen this in other clues).
'claim' becomes 'allege' (I've seen this before).
'involving' means one lot of letters goes inside another.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'allege' enclosing 'n' is 'allenge'.
(Other definitions for challenge that I've seen before include "Dispute the truth of", "difficult feat", "Difficult task", "Demanding or stimulating situation", "tackle", "Invitation to duel", "Issue an invitation to compete", "Invite to contest, throw down the gauntlet", "Take issue with" and "Ask to take part in a contest".)