Descendant admits returning for stinger (8)
I believe the answer is:
scorpion
'stinger' is the definition.
(I have seen 'Venomous stinger ' mean 'scorpion' so perhaps 'stinger' could also mean 'scorpion')
'descendant admits returning for' is the wordplay.
'descendant' becomes 'scion' (scion is a kind of descendant).
'admits' indicates putting letters inside.
'returning' shows that the letters should be reversed in order.
'for' becomes 'pro' (I've seen this before).
'pro' back-to-front is 'orp'.
'scion' placed around 'orp' is 'SCORPION'.
(Other definitions for scorpion that I've seen before include "Small spider with pincers and stinging tail" , "Poisonous thing" , "Venemous creature" , "Creature with a sting in its tail" , "Poisonous arachnid" .)