Old girl, condiment left out is repulsive (7)
I believe the answer is:
ogreish
'repulsive' is the definition.
Both the definition and answer are adjectives.
Maybe there's an association between them I don't understand?
'old girl condiment left out is' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'girl' becomes 'g'.
'condiment' becomes 'her' (I am not sure about this - if you are sure you should believe this answer much more).
'left' shows that the letters should be reversed in order.
'out' means one lot of letters goes inside another.
'her' written backwards gives 'reh'.
'reh' going around 'is' is 'reish'.
'o'+'g'+'reish'='OGREISH'
Can you help me to learn more?
(Other definitions for ogreish that I've seen before include "Looking like a fiend" , "Cruel and terrifying" , "Ugly" , "Monstrous, misshapen, cruel" , "Fearsome" .)