Professional supporter, English, being blasphemous (7)
I believe the answer is:
profane
'being blasphemous' is the definition.
(similar in meaning)
'professional supporter english' is the wordplay.
'professional' becomes 'pro' (abbreviation).
'supporter' becomes 'fan' (fan is a kind of supporter).
'english' becomes 'e' (abbreviation).
'pro'+'fan'+'e'='PROFANE'
(Other definitions for profane that I've seen before include "Secular, not religious" , "Sacrilegious or blasphemous" , "Unholy" , "Treat with irreverence" , "Irreverent - pagan" .)