Fear is no longer maintaining resistance (5)
I believe the answer is:
dread
'fear' is the definition.
(I know that fear can be written as dread)
'no longer maintaining resistance' is the wordplay.
'no longer' becomes 'dead' (I can't justify this - if you can you should believe this answer much more).
'maintaining' indicates putting letters inside (inserted letters are held or maintained).
'resistance' becomes 'r' (electronics abbreviation).
'dead' placed around 'r' is 'DREAD'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for dread that I've seen before include "Deep fear" , "Awe" , "Affright" , "Be scared of" , "Show horror" .)