English avoiding wooden ware getting expensive French plate (8)
'plate' is the definition.
(type of historical plate)
'english avoiding wooden ware getting expensive french' is the wordplay.
'english' becomes 'E' (abbreviation).
'avoiding' indicates named letters should be taken away.
'wooden ware' becomes 'treen' (treen can mean objects made of wood).
'getting' is a charade indicator (letters next to each other).
'expensive french' becomes 'cher'.
'treen' with 'e' removed is 'tren'.
(Other definitions for trencher that I've seen before include "Don cap", "Board", "one at digs?", "field worker", "Plate".)