Give up the role, as tricky (4,5)
I believe the answer is:
lose heart
'give up' is the definition.
(thesaurus)
'the role as tricky' is the wordplay.
'tricky' indicates anagramming the letters.
'the'+'role'+'as'='theroleas'
'theroleas' with letters rearranged gives 'LOSE HEART'.
(Other definitions for lose heart that I've seen before include "Become despondent" , "What patient may do before subsequent transplant" , "Mislay a card" , "Falter in courage - or fall in love? (4, 5)" , "Become disillusioned" .)