Merciless hustlers out to lunch (8)

I believe the answer is:

ruthless

'merciless' is the definition.
(similar in meaning)

'hustlers out to lunch' is the wordplay.
'out to lunch' indicates an anagram (out to lunch can mean mad).
'hustlers' anagrammed gives 'RUTHLESS'.

(Other definitions for ruthless that I've seen before include "Callous" , "Without pity or compassion" , "Having no mercy like hustlers" , "Showing no compassion" , "Without pity, merciless" .)

I've seen this clue in The Telegraph.

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