Advice helpful in the extreme? (3)
I believe the answer is:
tip
'advice' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tip that I've seen before include "for writers, it may be felt" , "End - pourboire" , "Warning" , "Helpful information; end" , "Clue" .)