No second turn for idiot (4)
I believe the answer is:
twit
'idiot' is the definition.
(I've seen this in other clues)
'no second turn' is the wordplay.
'no' suggests deleting specific letters.
'second' becomes 's' (common abbreviation).
'turn' becomes 'twist' (twisting is a kind of turning).
'twist' with 's' taken away is 'TWIT'.
'for' acts as a link.
(Other definitions for twit that I've seen before include "Silly person; tease" , "Slangily a foolish person" , "Stupid person" , "Bait - fool" , "Idiot; tease" .)