Possibly high and heroic, up flying (8)
I believe the answer is:
euphoric
'possibly high' is the definition.
(high can mean very happy)
'heroic up flying' is the wordplay.
'flying' indicates an anagram (letters fly around into new positions).
'heroic'+'up'='heroicup'
'heroicup' anagrammed gives 'EUPHORIC'.
'and' is the link.
(Other definitions for euphoric that I've seen before include "Over the moon?" , "Co-heir up for feeling excited and joyful" , "Travail" , "Elated, intensely happy" , "blissful result" .)