A girl dropping a line in Virginia lake (7)
I believe the answer is:
valerie
'a girl' is the definition.
'dropping a line in virginia lake' is the wordplay.
'dropping' says to take the initial letters (I've seen 'drop of' mean this).
'in' means one lot of letters goes inside another.
'virginia' becomes 'va' (US state abbreviation).
'lake' becomes 'erie' (Lake Erie is one of the Canadian/US 'Great Lakes').
The initial letter of 'line' is 'l'.
'va'+'erie'='vaerie'
'l' going inside 'vaerie' is 'VALERIE'.
(Another definition for valerie that I've seen is " Girl".)