Memorised last of story in the bar, drunk (2,5)
I believe the answer is:
by heart
'memorised' is the definition.
(knowing something by heart is memorising it)
'last of story in the bar drunk' is the wordplay.
'last of' indicates one should take the final letters.
'in' means one lot of letters goes inside another.
'drunk' indicates an anagram.
The final letter of 'story' is 'y'.
'the'+'bar'='thebar'
'thebar' is an anagram of 'bheart'.
'y' inserted inside 'bheart' is 'BY HEART'.
(Other definitions for by heart that I've seen before include "Committed to memory" , "Off pat" , "(Learnt) in memory" , "To know - - is to have in the memory" , "Thoroughly memorized, word perfect" .)