It's often said to be cutting (3)
I believe the answer is:
saw
'be cutting' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'it's often said' is the wordplay.
'it' becomes 'sa' (SA can mean sex appeal, as in 'it').
'often said' becomes 'w' (I can't explain this - if you can you should give a lot more credence to this answer).
'sa'+'w'='SAW'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for saw that I've seen before include "Implement for cutting wood" , "Saying; cut wood" , "Cutting blade" , "Perceived visually" , "Hand tool; proverb" .)