Grunge performed by elderly lead with a wheeze (4,4)

'wheeze' is the definition.
(wheeze can mean a scheme or good idea)

'grunge performed by elderly lead with a' is the wordplay.
'grunge' becomes 'goo' (grunge can mean goo or grime).
'performed by' becomes 'did' ('do' can be a synonym of 'perform'. I am not sure about the 'by' bit.).
'lead' says to take the initial letters.
'with' says to put letters next to each other.
The initial letter of 'elderly' is 'e'.
'goo'+'did'+'e'+'a'='GOOD IDEA'