Dressing? Many a one is getting a makeover (10)
I believe the answer is:
mayonnaise
'dressing?' is the definition.
(mayonnaise is a kind of dressing)
'many a one is getting a makeover' is the wordplay.
'getting' says to put letters next to each other.
'makeover' indicates an anagram (I've seen this in other clues).
'many'+'one'+'is'+'a'='manyoneisa'
'manyoneisa' anagrammed gives 'MAYONNAISE'.
(Other definitions for mayonnaise that I've seen before include "Salad dressing" , "Creamy dressing" , "which is saucy" , "7 for salad" , "Egg/oil sauce" .)