At no time is nerve lost (5)
I believe the answer is:
never
'at no time' is the definition.
(synonyms)
'nerve lost' is the wordplay.
'lost' indicates an anagram.
'nerve' anagrammed gives 'NEVER'.
'is' is the link.
(Other definitions for never that I've seen before include "Not ever" , "when hell freezes over?" , "when pigs fly" , "On no account" , "Not in a month of Sundays" .)