A hothead without weapons is innocuous! (8)

I believe the answer is:

harmless

'is innocuous' is the definition.
(synonyms)

'a hothead without weapons' is the wordplay.
'a hothead' becomes 'h' (head letter of 'hot').
'without weapons' becomes 'armless' ('weapon' can be 'arm' (synonyms) so maybe 'without weapons' can be ''armless').
'h'+'armless'='HARMLESS'

(Other definitions for harmless that I've seen before include "Benign, innocuous" , "Not producing any toxic effects" , "Innocuous, innocent" , "Not posing any danger" , "Not injurious" .)

I've seen this clue in the Evening Standard.

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