Lake taken in by extremely eager stranger (6)
I believe the answer is:
eerier
'stranger' is the definition.
(eerie means odd or strange)
'lake taken in by extremely eager' is the wordplay.
'lake' becomes 'erie' (Lake Erie is one of the Canadian/US 'Great Lakes').
'taken in by' indicates putting letters inside.
'extremely' suggests removing the centre (only the extremes of the word are used).
'eager' with its centre removed is 'er'.
'erie' placed within 'er' is 'EERIER'.
(Other definitions for eerier that I've seen before include "More strangely frightening" , "Stranger" , "More unsettling" , "More weird" , "More mysterious" .)