Friend is to help, we hear, with fence (8)
I believe the answer is:
palisade
'fence' is the definition.
('palisade' can be a synonym of 'fence')
'friend is to help we hear' is the wordplay.
'friend' becomes 'pal' (pal is a kind of friend).
'to help' becomes 'aide' (aide is a kind of help).
'we hear' indicates a 'sounds like' (homophone) clue.
'aide' sounds like 'ade'.
'pal'+'is'+'ade'='PALISADE'
'with' is the link.
(Other definitions for palisade that I've seen before include "Strong fence, for defence" , "Protecting fence" , "Stockade" , "Enclosure of stakes" , "A side lap (anag)" .)