Highly curious in past, prying ultimately (4)
I believe the answer is:
agog
'highly curious' is the definition.
'past prying ultimately' is the wordplay.
'past' becomes 'ago' (similar in meaning).
'ultimately' suggests the final letters.
The last letter of 'prying' is 'g'.
'ago'+'g'='AGOG'
'in' acts as a link.
(Other definitions for agog that I've seen before include "Expectant, eager" , "Very eager (to see/hear)" , "with eyes on stalks" , "Eager, avid" , "Enthusiastic" .)