Marine life trapped by undersea glaciers rising (5)
I believe the answer is:
algae
'marine life' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'trapped by undersea glaciers rising' is the wordplay.
'ALGAE' is hidden back-to-front in amongst the letters.
But, I'm unsure how this is indicated.
Can you help me to learn more?
(Other definitions for algae that I've seen before include "They grow near water and don't have ordinary roots or leaves" , "Type of seaweed" , "Seaweeds generally" , "Simple organisms, e.g. seaweeds" , "Water plants seen in a gale" .)