Counter is covered by others (6)
I believe the answer is:
resist
'counter' is the definition.
(thesaurus)
'is covered by others' is the wordplay.
'covered by' indicates putting letters inside.
'others' becomes 'rest' (I've seen this before**).
'is' put within 'rest' is 'RESIST'.
(Other definitions for resist that I've seen before include "Fight back" , "turn down" , "Forgo" , "Check; withstand" , "Bar" .)