Blunder about one Republican's tall animal (7)
I believe the answer is:
giraffe
'tall animal' is the definition.
(giraffes are tall animals)
'blunder about one republican's' is the wordplay.
'blunder' becomes 'gaffe' (gaffe is a kind of blunder).
'about' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'republican' becomes 'R' (abbreviation in US politics).
'i'+'r'='ir'
'gaffe' going around 'ir' is 'GIRAFFE'.
(Other definitions for giraffe that I've seen before include "Tallest mammal" , "The largest ruminant" , "Long-necked ruminant" , "Long - necked animal" , "Long-necked mammal" .)