Purpose English favour, heading off making effort (9)
I believe the answer is:
endeavour
'effort' is the definition.
(synonyms)
'purpose english favour heading off' is the wordplay.
'purpose' becomes 'end' (both can mean a goal).
'english' becomes 'E' (abbreviation).
'heading off' means to remove the first letter.
'favour' with its initial letter removed is 'avour'.
'end'+'e'+'avour'='ENDEAVOUR'
'making' acts as a link.
(Other definitions for endeavour that I've seen before include "Enterprise; earnest effort" , "Strive - over a nude (anag)" , "famous ship" , "First space shuttle to visit the International Space Station" , "Try hard (to achieve)" .)