Crossword Genius

Henry Percy developed a secret code (6)

Ross

I believe the answer is:

cypher

'a secret code' is the definition.
('cypher' can be a synonym of 'secret code')

'henry percy developed' is the wordplay.
'henry' becomes 'h' ('H' can be a synonym of 'henry').
'developed' is an anagram indicator.
'h'+'percy'='hpercy'
'hpercy' anagrammed gives 'CYPHER'.

(Other definitions for cypher that I've seen before include "Secret code (variant spelling)" , "Code; unimportant person" , "Secret way of writing" .)

I've seen this clue in The Independent.
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