Figure Greek character right to interrupt repast (7)
I believe the answer is:
numeral
'figure' is the definition.
(I've seen this in another clue)
'greek character right to interrupt repast' is the wordplay.
'greek character' becomes 'nu' (letter from the Greek alphabet).
'right' becomes 'r' (abbreviation).
'to interrupt' means one lot of letters goes inside another.
'repast' becomes 'meal' (synonyms).
'r' going within 'meal' is 'meral'.
'nu'+'meral'='NUMERAL'
(Other definitions for numeral that I've seen before include "Symbol used to express quantity" , "one involved in maths?" , "Rule man (anag) - digit" , "Mathematical figure" , "Figure representing a value" .)