Writer and cartoonist depicts three heads of state seen around European organisation (5)
I believe the answer is:
seuss
'writer and cartoonist depicts three' is the definition.
I can't judge whether this definition defines the answer.
'heads of state seen around european organisation' is the wordplay.
'heads of' indicates taking the first letters.
'around' means one lot of letters goes inside another.
'european' becomes 'E' (abbreviation e.g. EU).
'organisation' becomes 'us' (U.S. is an example).
The first letters of 'state seen' is 'ss'.
'e'+'us'='eus'
'ss' placed around 'eus' is 'SEUSS'.
Can you help me to learn more?
(Other definitions for seuss that I've seen before include "Dr -, children's author (The Cat in the Hat)" , "Dr. --, US children's author" , "8 [DOCTOR]" .)