Fender includes one narrow part (6)
I believe the answer is:
strait
'narrow part' is the definition.
'strait' can be an answer for 'narrow' (I've seen this before). I am unsure of the 'part' bit.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for strait that I've seen before include "Narrow sea-channel" , "Narrow stretch of sea" , "Narrow passage joining two large areas of water" , "Narrow sorts of traits" , "Hardship - narrow passage of water" .)