Small falcon in pursuit (5)
I believe the answer is:
hobby
This clue is a double definition.
'small falcon' is the first definition.
(I've seen this before)
'pursuit' is the second definition.
(I know that hobby is a class)
'in' acts as a link.
(Other definitions for hobby that I've seen before include "Bird - eg bird-watching" , "Raptor - pastime" , "Small falcon" , "activity giving pleasure" , "interest" .)