Left in place old Disney character (5)
I believe the answer is:
pluto
'disney character' is the definition.
(I've seen this before)
'left in place old' is the wordplay.
'left' becomes 'L' (common abbreviation).
'in' means one lot of letters goes inside another.
'place' becomes 'put' (synonyms).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'l' put into 'put' is 'plut'.
'plut'+'o'='PLUTO'
(Other definitions for pluto that I've seen before include "Ninth planet of solar system" , "Minor planet" , "Greek lord of the underworld, and a planet" , "Dis" , "Solar System's smallest planet" .)