Routine supporting Irish freedom fighter perhaps (9)
I believe the answer is:
irregular
'freedom fighter perhaps' is the definition.
I can't judge whether this defines the answer.
'routine supporting irish' is the wordplay.
'routine' becomes 'regular' (similar in meaning).
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'irish' becomes 'IR' (abbreviation for Irish).
'regular' put after 'ir' is 'IRREGULAR'.
Can you help me to learn more?
(Other definitions for irregular that I've seen before include "commonest verbs?" , "one of Holmes's Baker Street urchins" , "Haphazard" , "Unpunctual" , "Out of the ordinary" .)