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' going inside 'bass' is 'BIOMASS'.
'of' is the 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]" .)