Possible Belfast firm that is preserving singular cooking method (7)
I believe the answer is:
nicoise
'cooking method' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'possible belfast firm that is preserving singular' is the wordplay.
'possible belfast' becomes 'ni' (Belfast is the capital of Northern Ireland. I am not sure about the 'possible' bit.).
'firm' becomes 'co' (a firm is a company).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'preserving' is an insertion indicator.
'singular' becomes 's' (abbreviation in grammar).
'ie' enclosing 's' is 'ise'.
'ni'+'co'+'ise'='NICOISE'
Can you help me to learn more?