Film performance certainly not special (7)
I believe the answer is:
feature
'film' is the definition.
(feature-length film)
'performance certainly not special' is the wordplay.
'performance' becomes 'feat' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'certainly' becomes 'sure' (synonyms).
'not' indicates named letters should be taken away.
'special' becomes 'S' (common abbreviation as in Special Air Service).
'sure' with 's' taken out is 'ure'.
'feat'+'ure'='FEATURE'
Can you help me to learn more?
(Other definitions for feature that I've seen before include "Special attraction" , "Focal point" , "Quality" , "Magazine article" , "Principal film or non-news article" .)