Short coat given to old philosopher (5)
I believe the answer is:
plato
'philosopher' is the definition.
(Plato is an example)
'short coat given to old' is the wordplay.
'short coat given' becomes 'plat' (I am not sure about this - if you are sure you should believe this answer much more).
'to old' becomes 'o' (common abbreviation eg in OE for Old English).
'plat'+'o'='PLATO'
Can you help me to learn more?
(Other definitions for plato that I've seen before include "Greek philosopher, disciple of Aristotle" , "Greek character" , "Republican writer?" , "To pal up with Greek philosopher" , "Ancient Greek philosopher" .)