Unpleasant person in bother over weird pet (7)
I believe the answer is:
reptile
'unpleasant person' is the definition.
'bother over weird pet' is the wordplay.
'bother' becomes 'rile' (synonyms).
'over' means one lot of letters goes inside another.
'weird' is an anagram indicator.
'pet' with letters rearranged gives 'ept'.
'rile' going around 'ept' is 'REPTILE'.
'in' acts as a link.
(Other definitions for reptile that I've seen before include "Turtle, for example" , "eg Crocodile" , "Lizard, for example" , "Eg, snake, lizard, etc" , "Turtle or snake say" .)