A hybrid type of clue (6)
I believe the answer is:
across
'type of clue' is the definition.
(in a crossword)
'a hybrid' is the wordplay.
'hybrid' becomes 'cross' (cross between two things).
'a'+'cross'='ACROSS'
(Other definitions for across that I've seen before include "Clues like this" , "sort of clue?" , "Transverse" , "From side to side of (something)" , "Horizontally" .)