Crossword Genius

Cut oxygen, say, then hydrogen (4)

Ross

I believe the answer is:

gash

'cut' is the definition.
(I've seen this before)

'oxygen say then hydrogen' is the wordplay.
'oxygen say' becomes 'gas' (oxygen is a kind of gas).
'then' means one lot of letters go next to another.
'hydrogen' becomes 'h' (H is the chemical symbol for hydrogen).
'gas'+'h'='GASH'

(Other definitions for gash that I've seen before include "injury" , "Cut; waste (colloq.)" , "extra" , "score heavily" , "Long deep slash" .)

I've seen this clue in The Telegraph.
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