Crossword Genius

Underground room I see said to be difficult to understand (7)

Ross

I believe the answer is:

cryptic

'be difficult to understand' is the definition.
(as in a cryptic message)

'underground room i see said' is the wordplay.
'underground room' becomes 'crypt' (I've seen this before).
'said' shows a homophone (sound like).
'see' sounds like 'c'.
'crypt'+'i'+'c'='CRYPTIC'

'to' acts as a link.

(Other definitions for cryptic that I've seen before include "Like our other puzzle" , "(Of crossword) withindirect clues" , "Esoteric" , "Mysteriously obscure" , "Enigmatic" .)

I've seen this clue in The Telegraph.
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