One cared and isn't, I fancy, selfish (13)
I believe the answer is:
inconsiderate
'selfish' is the definition.
('inconsiderate' is associated in meaning with 'selfish')
'one cared and isn't i fancy' is the wordplay.
'and' says to put letters next to each other.
'fancy' indicates anagramming the letters.
'one'+'cared'+'isnt'+'i'='onecaredisnti'
'onecaredisnti' is an anagram of 'INCONSIDERATE'.
(Other definitions for inconsiderate that I've seen before include "Unkind" , "Thoughtless, rash" , "Heedless" , "Thoughtlessly hurtful" , "Lacking thought for others" .)