Ran into less extreme opposition - a growl (5)
I believe the answer is:
snarl
'a growl' is the definition.
(I've seen this in another clue)
'ran into less extreme opposition' is the wordplay.
I cannot really understand how this works, but
an anagram of 'ran' is 'nar' which is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for snarl that I've seen before include "Entangle wool - show displeasure" , "Growl viciously" , "Growl in a threatening manner" , "Growl aggressively" , "Tangle; growl" .)