Oklahoma's second-largest city (5)
I believe the answer is:
tulsa
'oklahoma's second-largest city' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tulsa that I've seen before include "part of Oklahoma" , "A lust for the Oklahoma oil city?" , "US city" , "OK city" , "City in Oklahoma featured in a 60s song" .)