Fool taking ecstasy twice and joint regularly (5)
I believe the answer is:
eejit
'fool' is the definition.
(I've seen this before)
'ecstasy twice and joint regularly' is the wordplay.
'ecstasy' becomes 'E' (informal term for the drug).
'twice' says to double the letters.
'and' means one lot of letters go next to another.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'joint' are 'jit'.
'e' duplicated is 'ee'.
'ee'+'jit'='EEJIT'
'taking' acts as a link.
(Other definitions for eejit that I've seen before include "Stupid type" , "Scottish (or Irish) twerp" , "lemon" , "(Scottish or Irish) fool" , "mug in Mayo" .)