Changed speed or rested (7)
I believe the answer is:
reposed
'rested' is the definition.
('repose' can be a synonym of 'rest')
'changed speed or' is the wordplay.
'changed' indicates an anagram.
'speed'+'or'='speedor'
'speedor' anagrammed gives 'REPOSED'.
(Other definitions for reposed that I've seen before include "What's settled" , "Rested" , "modelled afresh" , "Relaxed" .)