A tender time in Barking is unknown (13)
I believe the answer is:
indeterminate
'unknown' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'a tender time in barking' is the wordplay.
'barking' indicates an anagram (UK slang for mad).
'a'+'tender'+'time'+'in'='atendertimein'
'atendertimein' is an anagram of 'INDETERMINATE'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for indeterminate that I've seen before include "uncertain result?" , "Unfixed, uncertain" , "Having no fixed value" , "Not exactly defined" , "Vague - unsettled" .)