Friends out of steam (5)
I believe the answer is:
mates
'friends' is the definition.
(mate is a kind of friend)
'out of steam' is the wordplay.
'out of' indicates anagramming the letters.
'steam' anagrammed gives 'MATES'.
(Other definitions for mates that I've seen before include "Partners or pals" , "Friends among the ship's officers" , "Husbands, wives or pals" , "Pals or spouses" , "Pals or married couples" .)