Project on English fibre (4)
I believe the answer is:
jute
'fibre' is the definition.
(jute is a kind of fibre)
'project on english' is the wordplay.
'project' becomes 'jut' (I've seen this before).
'on' means one lot of letters go next to another.
'english' becomes 'e' (abbreviation).
'jut'+'e'='JUTE'
(Other definitions for jute that I've seen before include "Sacking plant; old tribesman" , "Plant - member of a Germanic tribe - fibre" , "Strong fibre" , "fibrous plant" , "Old invader of England" .)