Sage, for example, employed by Father Brown (4)
I believe the answer is:
herb
'sage for example' is the definition.
(I know that sage is a type of herb)
'employed by father brown' is the wordplay.
'employed by' says the answer is hidden in the clue.
'HERB' is hidden within 'father brown'.
(Other definitions for herb that I've seen before include "Bouquet garni component" , "bay perhaps" , "Chives or coriander, say" , "Maybe sage" , "Savoury plant" .)