Robin had a house to do up (4)
I believe the answer is:
hood
'robin' is the definition.
(I've seen this in other clues)
'a house to do up' is the wordplay.
'a house' becomes 'h'.
'to do' becomes 'doo' (I can't explain this - if you can you should believe this answer much more).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'doo' back-to-front is 'ood'.
'h'+'ood'='HOOD'
'had' acts as a link.
Can you help me to learn more?
(Other definitions for hood that I've seen before include "Head covering or American car bonnet" , "Outlaw and gangster" , "Protective cover - violent criminal (slang)" , "Capital cover" , "academic garment" .)