Claim a strand of hair twisted up (6)
I believe the answer is:
assert
'claim a strand' is the definition.
'assert' can be an answer for 'claim' (I've seen this in another clue). I am not sure about the 'a strand' bit.
'hair twisted up' is the wordplay.
'hair' becomes 'tress' (tress is a kind of hair).
'twisted' becomes 'a' (I can't explain this - if you can you should believe this answer much more).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'tress'+'a'='tressa'
'tressa' backwards is 'ASSERT'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for assert that I've seen before include "Declare, claim" , "Express forcibly" , "Confidently say" , "State firmly and with conviction" , "Aver, declare" .)