On reflection, being at home wearing raincoat is obsessive! (5)
I believe the answer is:
manic
'obsessive' is the definition.
(I've seen this before)
'on reflection being at home wearing raincoat' is the wordplay.
'on reflection' is a reversal indicator.
'being at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'wearing' indicates putting letters inside.
'raincoat' becomes 'mac' (macintosh is a type of raincoat).
'in' backwards is 'ni'.
'ni' going within 'mac' is 'MANIC'.
'is' acts as a link.
(Other definitions for manic that I've seen before include "Frenzied" , "Wildly excited" , "Insane" , "Hectic" , "Showing wild excitement" .)