Ball of yarn with tangle of hair twice brushed up (6)
I believe the answer is:
pompom
'ball' is the definition.
(I've seen this before)
'hair twice brushed up' is the wordplay.
'hair twice' means two substitutions for 'hair'.
'hair' becomes 'mop' (mop can mean a mass of hair).
'hair' becomes 'mop' (mop can mean a mass of hair).
'brushed up' shows that the letters should be reversed in order (in a down clue, letters go up).
'mop'+'mop'='mopmop'
'mopmop' reversed gives 'POMPOM'.
'of yarn with tangle of' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for pompom that I've seen before include "Decorative ball of tufted wool" , "fluffy decoration" , "Hat ornament" , "Fluffy ball - type of gun" , "Top decoration" .)