Club gets convict into hellish upset (10)
I believe the answer is:
Here is my best explanation:
'club' is the definition.
(shillelagh is a kind of club)
'convict into hellish upset' is the subsidiary indication.
'convict' becomes 'lag' (I've seen this in other clues).
'into' is an insertion indicator.
'upset' is an anagram indicator.
'hellish' is an anagram of 'shilleh'.
'lag' put within 'shilleh' is 'shillelagh'.
'gets' is the link.
(Other definitions for shillelagh that I've seen before include "Irish cudgel" and "Irish club".)