Will and Henry messing with poor Eddy (9)
I believe the answer is:
whirlpool
'eddy' is the definition.
(synonyms)
'will and henry messing with poor' is the wordplay.
'and' is a charade indicator (letters next to each other).
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'messing with' is an anagram indicator.
'will' after 'h' is 'hwill'.
'hwill' anagrammed with 'poor' gives 'WHIRLPOOL'.
(Other definitions for whirlpool that I've seen before include "Powerful circular current of water" , "Violent circular eddy of water" , "Strong circular current" , "Quickly rotating mass of water" .)