Try ales with 50 per cent off, perhaps (5)
I believe the answer is:
essay
'try' is the definition.
(essay can mean to try or attempt something)
'ales with 50 per cent off perhaps' is the wordplay.
'with 50 per cent off' suggests halving the letters.
'perhaps' becomes 'say' (both can mean 'for example').
'ales' cut in half is 'es'.
'es'+'say'='ESSAY'
(Other definitions for essay that I've seen before include "School composition" , "Attempt; written piece" , "Make an effort or attempt" , "Have a shot at a written piece" , "Composition, paper, article" .)