Knotty construction in clues, this shows what tons will also do (5-4)
I believe the answer is:
turks-head
'clues this shows what tons will also do' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'knotty construction' is the wordplay.
'knotty' becomes 'turks' (I can't explain this - if you can you should give a lot more credence to this answer).
'construction' becomes 'head' (head is a kind of construction).
'turks'+'head'='TURKS-HEAD'
'in' is the link.
Can you help me to learn more?
(Another definition for turks-head that I've seen is " Ornamental knot".)