Slender bar (3)
I believe the answer is:
rod
'slender bar' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rod that I've seen before include "Thin straight bar" , "that most anglers use" , "16.5 feet" , "- - , pole or perch" , "Baton, pole" .)