Impatient tourist on vacation tucking into fish (5)
I believe the answer is:
ratty
'impatient' is the definition.
(thesaurus)
'tourist on vacation tucking into fish' is the wordplay.
'on vacation' means to remove the middle letters.
'tucking into' is an insertion indicator.
'fish' becomes 'ray' (ray is a kind of fish).
'tourist' with its centre taken out is 'tt'.
'tt' placed within 'ray' is 'RATTY'.
(Other definitions for ratty that I've seen before include "Cross - character in "The Wind in the Willows"" , "with pests" , "with hump?" , "Waspish" , "Bad-tempered, irritable as a rodent" .)