Has to knot a piece of rope in a certain form (5)
I believe the answer is:
shape
'form' is the definition.
(I know that form can be written as shape)
'has to knot a piece of rope in a certain' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'has' is 'sha' which is located in the answer.
'piece' could be 'p' (abbreviation for Pawn) and 'p' is found within the answer.
A single letter 'e' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for shape that I've seen before include "Mould into new phase" , "Control development of" , "Square, circle, etc." , "Good physical form" , "Heaps (anag.)" .)