A sort of steam friends (5)

I believe the answer is:

mates

'friends' is the definition.
(I know this)

'a sort of steam' is the wordplay.
'a sort of' indicates an anagram.
'steam' is an anagram of 'MATES'.

(Other definitions for mates that I've seen before include "Friends among the ship's officers" , "Pals or married couples" , "conclusive moves on board" , "Chums" , "Pals, pairs" .)

I've seen this clue in the Sydney Morning Herald.

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