Welsh in Green EU organisation (7)
I believe the answer is:
renegue
'welsh' is the definition.
(I've seen this before)
'green eu organisation' is the wordplay.
'organisation' indicates an anagram.
'green'+'eu'='greeneu'
'greeneu' is an anagram of 'RENEGUE'.
'in' is the link.
(Other definitions for renegue that I've seen before include "Break a promise" , "Deny" , "Go back on one's word" , "Rue gene (anag.)" , "Go back on (a promise)" .)