Bad-tempered person driving taxi across river (6)
I believe the answer is:
crabby
'bad-tempered' is the definition.
(synonyms)
'person driving taxi across river' is the wordplay.
'person driving taxi' becomes 'cabby' (cab driver).
'across' means one lot of letters goes inside another.
'river' becomes 'r' (abbreviation for river).
'cabby' going around 'r' is 'CRABBY'.
(Other definitions for crabby that I've seen before include "Grumpy like crustacean" , "like one playing with sea? Just so" , "Bad-tempered like common crustacean" , "like a hermit?" , "Ill-tempered" .)