Tip for polishing dirty set of books is well advised (7)
I believe the answer is:
prudent
'well advised' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives can sometimes mean the same thing.
'tip for polishing dirty set of books' is the wordplay.
'tip for' suggests taking the first letters (one end or tip of the word).
'dirty' becomes 'rude' (I've seen this before).
'set of books' becomes 'NT' (New Testament).
The first letter of 'polishing' is 'p'.
'p'+'rude'+'nt'='PRUDENT'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for prudent that I've seen before include "Thinking of the future" , "Acting with care for the future" , "Careful, circumspect" , "Wise and cautious" , "Judicious" .)