They grip and hold on in the last resort (6)
I believe the answer is:
talons
'they grip and hold' is the definition.
The definition suggests an adverb but the answer is not.
'on in the last resort' is the wordplay.
'in' means one lot of letters goes inside another.
'resort' is an anagram indicator (re-sort the letters).
'last' with letters rearranged gives 'tals'.
'on' put into 'tals' is 'TALONS'.
Can you help me to learn more?
(Other definitions for talons that I've seen before include "Sharply hooked claws" , "Claws of a bird" , "Hooked claws of birds of prey" , "Sharp hooked claws" .)