Unsheathe and turn to parry with (4)
I believe the answer is:
draw
'unsheathe' is the definition.
(thesaurus)
'turn to parry with' is the wordplay.
'turn' shows that the letters should be reversed in order.
'to parry' becomes 'ard' (I can't explain this - if you can you should believe this answer much more).
'with' becomes 'w' (abbreviation).
'ard' back-to-front is 'dra'.
'dra'+'w'='DRAW'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for draw that I've seen before include "Take in (a breath), attraction" , "Design" , "Snag" , "Tie - attract" , "Extract" .)