Two princes and an unknown in formation (7)
I believe the answer is:
phalanx
'formation' is the definition.
The answer and definition can be both groups as well as being singular nouns.
Maybe there's a link between them I don't understand?
'two princes and an unknown' is the wordplay.
'two princes' can mean two substitutions for 'prince'.
'prince' becomes 'p' (abbreviation).
'prince' becomes 'hal' (Shakespearean nickname of Henry V when a prince).
'and' is a charade indicator (letters next to each other).
'unknown' becomes 'x' (algebra).
'p'+'hal'+'an'+'x'='PHALANX'
'in' is the link.
Can you help me to learn more?
(Other definitions for phalanx that I've seen before include "Packed crowd of people" , "Solid body of men" , "Close mass of fighters" , "Compact infantry mass; finger bone" , "Body of troops in close formation" .)