Born to talk banally about methane, say (7,3)
I believe the answer is:
natural gas
'methane say' is the definition.
(natural gas often contains methane)
'born to talk banally' is the wordplay.
'born' becomes 'natural' (similar in meaning).
'to talk banally' becomes 'gas' (gas can mean to talk nonsense).
'natural'+'gas'='NATURAL GAS'
'about' is the link.
(Other definitions for natural gas that I've seen before include "Fuel from eg 2 down" , "Fuel from underground" , "Energy source from underground" .)