A line of questionable length (6)
I believe the answer is:
string
'a line' is the definition.
(I know that string is a type of cord)
'questionable length' is the wordplay.
I cannot quite understand how this works, but
'length' could be 'r' (r is a kind of length) and 'r' is present in the answer.
The remaining letters 'sting' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for string that I've seen before include "Series of events" , "Piece of catgut stretched on violin" , "Something for tying up" , "A lightweight cord" , "This vest is made of large mesh" .)