Some discover Montana, a state (7)
I believe the answer is:
vermont
'state' is the definition.
(Vermont is an example)
'some discover montana a' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'VERMONT' is hidden in the letters of 'discover montana a'.
(Other definitions for vermont that I've seen before include "US state, named for the Green Mountains" , "The Green Mountain state" , "New England state, capital Montpelier" .)