Directed mark of error to be placed in dictionary (5)
I believe the answer is:
coxed
'directed' is the definition.
(acted as a cox on a boat)
'mark of error to be placed in dictionary' is the wordplay.
'mark of error' becomes 'X' (mark placed next to error, opposite of a tick).
'to be placed in' is an insertion indicator (I've seen this in other clues).
'dictionary' becomes 'COED' (Concise Oxford English Dictionary).
'x' placed into 'coed' is 'COXED'.
(Other definitions for coxed that I've seen before include "Guided, say, four" , "Having a helmsman" , "Steered (a rowing boat)" .)