Piece of fluff seen in a tuft of wool (9)
I believe the answer is:
flintlock
'piece' is the definition.
(flintlock is a kind of piece)
'fluff seen in a tuft of wool' is the wordplay.
'fluff' becomes 'lint' (I've seen this in another clue).
'seen in' means one lot of letters goes inside another.
'a tuft of wool' becomes 'flock' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lint' placed into 'flock' is 'FLINTLOCK'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for flintlock that I've seen before include "Type of firearm" , "Piece of old" , "gun" , "Weapon" , "Old musket" .)