A second month in profit for energy supplier (3,4)
I believe the answer is:
gas main
'energy supplier' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'a second month in profit' is the wordplay.
'second' becomes 's' (common abbreviation).
'month' becomes 'M' (standard abbreviation).
'in' indicates putting letters inside.
'profit' becomes 'gain' (synonyms).
'a'+'s'+'m'='asm'
'asm' put inside 'gain' is 'GAS-MAIN'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for gas main that I've seen before include "Important energy distributor -- Ian's mag (anag)" , "pipework" , "Fuel supply" , "Large pipe delivering domestic energy source" , "Domestic fuel pipeline" .)