Henry and Nick forming barrier (5)
I believe the answer is:
hedge
'barrier' is the definition.
(I know that hedge is a type of fence)
'henry and nick' is the wordplay.
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'and' means one lot of letters go next to another.
'nick' becomes 'edge' (I can't explain this - if you can you should believe this answer much more).
'h'+'edge'='HEDGE'
'forming' is the link.
Can you help me to learn more?
(Other definitions for hedge that I've seen before include "take evasive action" , "Fence formed by bushes" , "Avoid making a definite commitment" , "appear non-committal in statement" , "Living barrier" .)