Tiny scuffle involved restraining one adequately (12)
I believe the answer is:
sufficiently
'adequately' is the definition.
('sufficiently' can be a synonym of 'adequately')
'tiny scuffle involved restraining one' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'restraining' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'tiny'+'scuffle'='tinyscuffle'
'tinyscuffle' is an anagram of 'suffciently'.
'suffciently' enclosing 'i' is 'SUFFICIENTLY'.
(Another definition for sufficiently that I've seen is " Adequately".)