In general, an eel wriggles (3)
I believe the answer is:
lee
'in general' is the definition.
'Lee' can be an answer for 'general' (Robert E. Lee - US revolutionary commander). I'm unsure of the 'in' bit.
'an eel wriggles' is the wordplay.
'wriggles' indicates an anagram (letters wriggle around into new positions).
'eel' with letters rearranged gives 'LEE'.
Can you help me to learn more?
(Other definitions for lee that I've seen before include "The sheltered side of something" , "The sheltered side - of Cork's river?" , "Revolutionary general" , "Commander of the Confederate States Army in the American Civil War" , "Confederate general" .)