A lively horse galloped around in the best part of Peru (7)
I believe the answer is:
prancer
'a lively horse' is the definition.
(I've seen this before)
'galloped around in the best part of peru' is the wordplay.
'galloped' becomes 'ran' (I've seen this in other clues).
'around' becomes 'c' (abbreviation for 'circa').
'in the' is an insertion indicator.
'best part of peru' becomes 'per' (I can't justify this - if you can you should believe this answer much more).
'ran'+'c'='ranc'
'ranc' placed into 'per' is 'PRANCER'.
Can you help me to learn more?
(Other definitions for prancer that I've seen before include "A lively horse" , "Sleigh-puller" , "Spirited horse" , "One of Santa's reindeers" , "Xmas reindeer" .)