Lawsuit father's taken out of proportion (6)
I believe the answer is:
action
'lawsuit' is the definition.
(synonyms)
'father's taken out of proportion' is the wordplay.
'father' becomes 'fr' (abbreviation as in a priest's title).
'taken out of' is a deletion indicator.
'proportion' becomes 'fraction' (I've seen this before).
'fraction' with 'fr' removed is 'ACTION'.
(Other definitions for action that I've seen before include "skirmish" , "Lawsuit; something done" , "The process of doing something" , "Litigation" , "exploit" .)