Fit together small part to clamp old vacuum's lead (8)
I believe the answer is:
dovetail
'fit together' is the definition.
(thesaurus)
'small part to clamp old vacuum's lead' is the wordplay.
I cannot quite understand how this works, but
'part' could be 'tail' (tail is a kind of part) and 'tail' is located in the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dovetail that I've seen before include "Fit together well" , "Come together" , "Type of joint - fit closely together" , "Joint with fan-shaped tenon" , "Violated (anag) -- mortise joint" .)