Naturally, some sap gets the reins tangled (5)
I believe the answer is:
resin
'naturally some sap' is the definition.
'resin' can be an answer for 'sap' (I've seen this before). I am not sure about the 'naturally some' bit.
'the reins tangled' is the wordplay.
'tangled' indicates an anagram.
'reins' anagrammed gives 'RESIN'.
'gets' acts as a link.
Can you help me to learn more?
(Other definitions for resin that I've seen before include "Tree gum" , "Unprocessed pine secretion" , "Elemi, for example" , "Rinse out this substance from trees" , "It's obtained from tree-sap" .)