Foolish rugby player with sex appeal attends regularly (4-6)
I believe the answer is:
half-witted
'foolish' is the definition.
'rugby player with sex appeal attends regularly' is the wordplay.
'rugby player' becomes 'half' (short for half-back).
'with' becomes 'w' (abbreviation**).
'sex appeal' becomes 'it'.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'attends' are 'ted'.
'half'+'w'+'it'+'ted'='HALF-WITTED'
(Other definitions for half-witted that I've seen before include "Feebleminded" , "Stupid" .)