Crossword Genius

Letter about gas, I’m perplexed (5)

Ross

I believe the answer is:

sigma

'letter' is the definition.
(sigma is a kind of letter)

'gas im perplexed' is the wordplay.
'perplexed' indicates an anagram.
'gas'+'im'='gasim'
'gasim' anagrammed gives 'SIGMA'.

'about' acts as a link.

(Other definitions for sigma that I've seen before include "The 18th letter of the Greek alphabet" , "Eighteenth letter of the Greek alphabet" , "character abroad" , "Letter from Athens" , "local opening in Salonika" .)

I've seen this clue in The Telegraph.
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