Mythical creature Greek character picked up -- one with growth on foot? (7)
I believe the answer is:
unicorn
'mythical creature' is the definition.
(I've seen this before)
'greek character picked up one with growth on foot?' is the wordplay.
'greek character' becomes 'nu' (letter from the Greek alphabet).
'picked up' shows that the letters should be reversed in order.
'one' becomes 'i' (Roman numeral).
'with' means one lot of letters go next to another.
'growth on foot?' becomes 'corn' (corn can thickened skin on a foot).
'nu' back-to-front is 'un'.
'un'+'i'+'corn'='UNICORN'
(Other definitions for unicorn that I've seen before include "that's fabulous" , "Fabulous beast like one-horned horse" , "Mythical animal with one horn" , "Imaginary, horned horse-like creature" , "Lion's traditional adversary" .)