Remote lake Stanley finally found in expedition (8)
I believe the answer is:
outlying
'remote' is the definition.
(thesaurus)
'lake stanley finally found in expedition' is the wordplay.
'lake' becomes 'l'.
'finally' says to take the final letters.
'found in' indicates putting letters inside.
'expedition' becomes 'outing' ('outing' can be a synonym of 'expedition'**).
The final letter of 'stanley' is 'y'.
'l'+'y'='ly'
'ly' put inside 'outing' is 'OUTLYING'.
(Other definitions for outlying that I've seen before include "On the exterior" , "Away from the middle" , "Remote from the centre" , "remote area" .)