Resistance insufficiently worn down? (11)
I believe the answer is:
underground
'resistance' is the definition.
(I know that resistance can be written as underground)
'insufficiently worn down?' is the wordplay.
'insufficiently' becomes 'under' (I can't explain this - if you can you should believe this answer much more).
'worn down?' becomes 'ground' (ground down).
'under'+'ground'='UNDERGROUND'
Can you help me to learn more?
(Other definitions for underground that I've seen before include "Secret resistance movement" , "In hiding" , "Tube; covert" , "Hidden away" , "Travel on this" .)