Tidy writer keeps a note (5)
I believe the answer is:
preen
'tidy' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how one could define the other.
'writer keeps a note' is the wordplay.
'writer' becomes 'pen' (something which writes).
'keeps' is an insertion indicator (inserted letters are kept inside).
'a note' becomes 're' (as in do-re-mi).
'pen' going around 're' is 'PREEN'.
Can you help me to learn more?
(Other definitions for preen that I've seen before include "Groom with great care" , "Primp" , "Beautify" , "Groom (oneself) with evident vanity" , "Groom elaborately" .)