Endure being tender in A&E (5)
I believe the answer is:
abide
'endure' is the definition.
('abide' can be a synonym of 'endure')
'tender in ae' is the wordplay.
'tender' becomes 'bid' ('bid' can be a synonym of 'tender').
'in' indicates putting letters inside.
'bid' put into 'ae' is 'ABIDE'.
'being' is the link.
(Other definitions for abide that I've seen before include "Endure, tolerate" , "Stomach" , "brook" , "Accept" , "Tolerate - dwell" .)