Unusual play with Act 1 rewritten (8)
I believe the answer is:
atypical
'unusual' is the definition.
('atypical' can be a synonym of 'unusual')
'play with act 1 rewritten' is the wordplay.
'with' means one lot of letters go next to another.
'1' becomes 'i' (roman numeral).
'rewritten' indicates an anagram.
'play'+'act'+'i'='playacti'
'playacti' is an anagram of 'ATYPICAL'.
(Other definitions for atypical that I've seen before include "Unusual" , "Not as expected" , "Novel" , "'Abnormal, aberrant (8)'" , "Nonconforming" .)