Tried working when exhausted (5)
I believe the answer is:
tired
'exhausted' is the definition.
(exhausted can mean very tired)
'tried working' is the wordplay.
'working' indicates an anagram.
'tried' with letters rearranged gives 'TIRED'.
'when' is the link.
(Other definitions for tired that I've seen before include "Weary or fed up" , "Done in" , "Beat" , "Exhausted" , "Sleepy" .)