It's a revelation to one with great expectations trapped by wild hyena (8)
I believe the answer is:
epiphany
'it's a revelation' is the definition.
(thesaurus)
'one with great expectations trapped by wild hyena' is the wordplay.
'one with great expectations' becomes 'pip' (I can't explain this - if you can you should give a lot more credence to this answer).
'trapped by' indicates putting letters inside.
'wild' indicates an anagram.
'hyena' is an anagram of 'ehany'.
'pip' put inside 'ehany' is 'EPIPHANY'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for epiphany that I've seen before include "when the wise men bring gifts" , "Christian festival of Magi visiting Chirst, celebrated on 6th January" , "Moment of sudden revelation (involving three wise men from the east?)" , "January date" , "A devine manifestation" .)