Trouble with one consuming old mayonnaise (5)
I believe the answer is:
aioli
'mayonnaise' is the definition.
(mayonnaise seasoned with garlic)
'trouble with one consuming old' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'with' says to put letters next to each other.
'one' becomes 'i' (roman numeral).
'consuming' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'ail'+'i'='aili'
'aili' placed around 'o' is 'AIOLI'.
(Other definitions for aioli that I've seen before include "Dressing" , "A lamb joint; driven clouds" , "mayonniase" , "Mayonnaise with garlic" , "garlic sauce" .)