Welcome appeals by a conservation group (8)
I believe the answer is:
pleasant
'welcome' is the definition.
(thesaurus)
'appeals by a conservation group' is the wordplay.
'appeals' becomes 'pleas' (plea is a kind of appeal).
'by' is a charade indicator (letters next to each other).
'conservation group' becomes 'nt' (abbreviation for National Trust).
'pleas'+'a'+'nt'='PLEASANT'
(Other definitions for pleasant that I've seen before include "sweet?" , "Satisfying, likeable" , "Charming" , "Nice, satisfying" , "Attractive" .)