Friend grabbing horse to annoy marsupial (9)
I believe the answer is:
phalanger
'marsupial' is the definition.
(I know that Phalanger is a type of marsupial)
'friend grabbing horse to annoy' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'grabbing' is an insertion indicator.
'horse' becomes 'H' (abbreviation as in horse power).
'to annoy' becomes 'anger' (I've seen this before).
'pal' going around 'h' is 'phal'.
'phal'+'anger'='PHALANGER'
(Other definitions for phalanger that I've seen before include "Little Aussie's" , "Lemur-like creature" , "Marsupial" , "may be flying in Australia" .)