Bill in club, upset (3)
I believe the answer is:
Here is my best explanation:
'bill' is the definition.
(tab is a kind of bill)
'club upset' is the subsidiary indication.
'club' becomes 'bat' (bat is a kind of club).
'upset' is a reversal indicator.
'bat' backwards is 'tab'.
'in' is the link.
(Other definitions for tab that I've seen before include "Tally; flap", "Tally of orders in bar", "Tag", "Bar tally; small flap", "The bill in a restaurant", "Kind of label for bat", "Marker", "Text indent key", "Label" and "Drug".)