Heather has a way to be enduring (7)
I believe the answer is:
lasting
'be enduring' is the definition.
('lasting' can be similar in meaning to 'enduring')
'heather has a way' is the wordplay.
'heather' becomes 'ling' ('ling' can be a synonym of 'heather').
'has' is an insertion indicator.
'way' becomes 'st' (**).
'a'+'st'='ast'
'ling' going around 'ast' is 'LASTING'.
'to' is the link.
(Other definitions for lasting that I've seen before include "Abiding, durable" , "long-term" , "Enduring" , "Persistent" , "Permanent" .)