Staggering, Herculean power fills legendary Irish figure (10)
I believe the answer is:
leprechaun
'legendary irish figure' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'staggering herculean power fills' is the wordplay.
'staggering' indicates an anagram (letters stagger around).
'power' becomes 'p' (symbol in physics).
'fills' is an insertion indicator (one set of letters goes inside another).
'herculean' with letters rearranged gives 'lerechaun'.
'lerechaun' enclosing 'p' is 'LEPRECHAUN'.
Can you help me to learn more?
(Other definitions for leprechaun that I've seen before include "He helps Irish housewife" , "Elf in Irish folklore" , "Mischievous imp" , "Mischievous Irish sprite" , "Mischievous Irish elf" .)