Pike this old defence force employed (4,5)
I believe the answer is:
home guard
'pike this old defence' is the definition.
The definition suggests a singular noun which matches the answer.
'force employed' is the wordplay.
I cannot quite understand how this works, but
'force' could be 'guard' (guard is a kind of force) and 'guard' is present in the answer.
The remaining letters 'home' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for home guard that I've seen before include "Last line of defence in World War II" , "Volunteer force" , "security force" , "Dad's Army" , "World War Two defence organisation" .)