Gas meter almost broken by worker ... almost (7)
I believe the answer is:
methane
'gas' is the definition.
(methane is a gas)
'meter almost broken by worker almost' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'broken by' means one lot of letters goes inside another (inserted letters break into the word).
'worker' becomes 'hand' (hand is a kind of worker).
'almost' means to remove the last letter (most of the word but not all of it).
'meter' with its last letter taken off is 'mete'.
'hand' with its last letter taken off is 'han'.
'mete' going around 'han' is 'METHANE'.
(Other definitions for methane that I've seen before include "Combustible atmosphere" , "Flammable gas, CH4" , "Naturally occurring flammable gas" , "simplest hydrocarbon" , "Greenhouse gas produced by cows" .)