To do up and make tidy is something unusual (6)
I believe the answer is:
oddity
'something unusual' is the definition.
(I've seen this before)
'to do up and make tidy' is the wordplay.
'to do up' becomes 'od' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'make' indicates anagramming the letters.
'tidy' with letters rearranged gives 'dity'.
'od'+'dity'='ODDITY'
'is' is the link.
Can you help me to learn more?
(Other definitions for oddity that I've seen before include "Quality of strangeness" , "Strange person/thing" , "Strange occurrence, person or thing" , "Curious thing" , "Something out of the ordinary" .)