Unusually singular plant in Trafalgar Square (4)
I believe the answer is:
alga
'unusually singular plant' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'in trafalgar square' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ALGA' is hidden within 'trafalgar square'.
Can you help me to learn more?
(Other definitions for alga that I've seen before include "from ore found locally" , "Simple plant, plankton or seaweed say" , "Seaweed family group" , "Gala class of seaweed" , "Water plant for a gal" .)