A cable, at certain points, is heavy (6)
I believe the answer is:
leaden
'heavy' is the definition.
(I know that heavy can be written as leaden)
'a cable at certain points' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
'points' could be 'en' (compass points east and north) and 'en' is found in the answer.
The remaining letters 'led' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for leaden that I've seen before include "Describes grey overcast skies" , "Dull, heavy, slow" , "Slow-moving, being like heavy metal" , "Heavy - plodding" , "Heavy or slow, like dark-gray metal" .)