MO ready to impress City (6)
I believe the answer is:
recipe
'mo' is the definition.
(thesaurus)
'ready to impress city' is the wordplay.
'ready' becomes 'ripe' (similar in meaning).
'to impress' is an insertion indicator (impress can mean enlist or recruit).
'city' becomes 'EC' (the City of London postcode).
'ripe' placed around 'ec' is 'RECIPE'.
(Other definitions for recipe that I've seen before include "Pierce (anag) - directions" , "Directions for making a dish" , "List of ingredients" , "Cooking prescription" , "Kitchener's instructions" .)