Intercede, seeing back trouble is beginning to ease (6)
I believe the answer is:
liaise
'intercede' is the definition.
('liaise' can be a synonym of 'intercede')
'back trouble is beginning to ease' is the wordplay.
'back' is a reversal indicator.
'trouble' becomes 'ail' ('ail' can be a synonym of 'trouble').
'beginning to' says to take the initial letters.
The first letter of 'ease' is 'e'.
'ail' backwards is 'lia'.
'lia'+'is'+'e'='LIAISE'
'seeing' is the link.
(Other definitions for liaise that I've seen before include "make contact" , "Cooperate on a matter of mutual concern" , "Foster co-operation" , "exchange information" , "Work together" .)