Jolliest hotel applies heartlessly to evict Oscar (8)
I believe the answer is:
happiest
'jolliest' is the definition.
Both the answer and definition are superlative adjectives. Perhaps you can see an association between them that I can't see?
'hotel applies heartlessly to evict oscar' is the wordplay.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'applies heartlessly' becomes 'appies' (I can't explain this - if you can you should believe this answer much more).
'evict' indicates named letters should be taken away.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'to' with 'o' taken away is 't'.
'h'+'appies'+'t'='HAPPIEST'
Can you help me to learn more?
(Other definitions for happiest that I've seen before include "Most gay" , "extremely contented" , "Gladdest" , "Most content" , "Most contented and satisfied" .)