To glide freely at height can be a joy! (7)
I believe the answer is:
delight
'a joy' is the definition.
('delight' can be a synonym of 'joy')
'to glide freely at height' is the wordplay.
I cannot really see how this works, but
an anagram of 'glide' is 'delig' which is located in the answer.
'height' could be 'ht' (abbreviation) and 'ht' is found within the answer.
No letters remain.
This explanation may well be incorrect...
'can be' is the link.
Can you help me to learn more?
(Other definitions for delight that I've seen before include "Greensleeves was mine" , "Greatly please" , "Glee; its spirit rare, Shelley" , "Ecstasy" , "Felicity" .)