Animal carrying bug: extremely unusual weapon (8)
I believe the answer is:
catapult
'weapon' is the definition.
(I've seen this before)
'animal carrying bug extremely unusual' is the wordplay.
'animal' becomes 'cat' (I've seen this before**).
'carrying' indicates putting letters inside.
'bug' becomes 'tap' (I've seen this before).
'extremely' means to remove the middle letters.
'unusual' with its centre removed is 'ul'.
'tap'+'ul'='tapul'
'cat' placed around 'tapul' is 'CATAPULT'.
(Other definitions for catapult that I've seen before include "Aircraft carrier launcher" , "Stone-throwing weapon" , "Weapon for hurling stones" , "Stone thrower" , "Ballista" .)