The Spanish finally comb the river (4)
I believe the answer is:
elbe
'river' is the definition.
(river in Germany)
'the spanish finally comb the' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'finally' suggests the final letters.
The last letters of 'comb the' are 'be'.
'el'+'be'='ELBE'
(Other definitions for elbe that I've seen before include "River rising in the Czech Republic and flowing into the North Sea" , "River flowing through Dresden and Hamburg" , "River of Germany" , "Current" , "German banker" .)