Source of energy from Isle of Man fish stocks (7)
I believe the answer is:
biomass
'source of energy from isle' is the definition.
The definition suggests a singular noun which matches the answer.
'man fish stocks' is the wordplay.
'man' becomes 'iom' (abbreviation for Isle of Man).
'fish' becomes 'bass' (bass is a kind of fish).
'stocks' means one lot of letters goes inside another.
'iom' put into 'bass' is 'BIOMASS'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for biomass that I've seen before include "Organic source of energy" , "Measure of living organisms" , "source of 8 [RENEWABLE ENERGY]" .)