Cheers for hare sent astray (8)
I believe the answer is:
heartens
'cheers' is the definition.
('hearten' can be a synonym of 'cheer')
'hare sent astray' is the wordplay.
'astray' indicates anagramming the letters.
'hare'+'sent'='haresent'
'haresent' with letters rearranged gives 'HEARTENS'.
'for' acts as a link.
(Other definitions for heartens that I've seen before include "Encourages in cardiac way" , "Cheers up, gives courage to" , "Cheers, gives hope to" .)