European head traversing lake with soldier (7)
I believe the answer is:
belgian
'european' is the definition.
(I know that Belgian is a type of european)
'head traversing lake with soldier' is the wordplay.
'head' becomes 'bean' (bean is a kind of head).
'traversing' indicates putting letters inside.
'lake' becomes 'L' (geographical abbreviation).
'with' says to put letters next to each other.
'soldier' becomes 'GI' (term for US soldier).
'l'+'gi'='lgi'
'bean' enclosing 'lgi' is 'BELGIAN'.
(Other definitions for belgian that I've seen before include "Bengali from a European state?" , "Eg, Brussels native" , "One from Liege, say" , "Hercule Poirot's nationality" , "Nationality of Rene Magritte" .)