Peaceful -- or perhaps loco? (7)
I believe the answer is:
pacific
I believe this is a double definition.
'peaceful' is the first definition.
(similar in meaning)
'perhaps loco?' is the second definition.
(Pacific is a type of locomotive)
'or' acts as a link.
(Other definitions for pacific that I've seen before include "Largest ocean" , "Conciliatory - calm" , "Calm - sea" , "water" , "Non-combatant" .)