Thick strings (5)
I believe the answer is:
cords
'thick strings' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cords that I've seen before include "Pieces of twine, say" , "Trousers of ribbed cloth" , "Electric flexes" , "Flexes; trousers" , "Velvety trousers" .)