Stale hero prepared to give up (4,5)
I believe the answer is:
lose heart
'give up' is the definition.
(thesaurus)
'stale hero prepared' is the wordplay.
'prepared' indicates an anagram.
'stale'+'hero'='stalehero'
'stalehero' anagrammed gives 'LOSE HEART'.
'to' acts as a link.
(Other definitions for lose heart that I've seen before include "Let hopes dwindle - real ethos involved" , "Become disillusioned" , "Mislay a card" , "Become despondent" , "What patient may do before subsequent transplant" .)