At first, Jimi Hendrix regularly shown to be forceful character? (4)
I believe the answer is:
jedi
'to be forceful character?' is the definition.
(the Jedi use the Force in the Star Wars films)
'at first jimi hendrix regularly' is the wordplay.
'at' says to put letters next to each other.
'first jimi' becomes 'j' (1st letter of 'jimi').
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'hendrix' are 'edi'.
'j'+'edi' is 'JEDI'.
'shown' acts as a link.
(Other definitions for jedi that I've seen before include "Star Wars knights" , "Forceful people in films" , "Film: 'Return of the --'" , "Forceful knight" , "Star Wars warrior" .)