A knotty snag (5)
I believe the answer is:
hitch
'snag' is the definition.
(synonyms)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for hitch that I've seen before include "Setback" , "Snag, drawback" , "Make fast" , "Unexpected problem" , "Tether (rope); difficulty" .)