Turn of phrase did I omit to employ? (5)
I believe the answer is:
idiom
'turn of phrase' is the definition.
(I've seen this before)
'did i omit to employ?' is the wordplay.
'to employ?' indicates a hidden word (the answer's letters are employed by the clue).
'IDIOM' can be found hidden inside 'did i omit'.
(Other definitions for idiom that I've seen before include "Colloquialism" , "characteristic use of language" , "Expression that does not make literal sense" , "Style of speaking characteristic of a specific group" , "Manner of speaking or writing" .)