Room for preparing all we know, longing to intervene (7)
I believe the answer is:
kitchen
'room for preparing' is the definition.
(room for preparing food)
'all we know longing to intervene' is the wordplay.
'all we know' becomes 'ken' (the range of someone's knowledge).
'longing' becomes 'itch' (I've seen this before).
'to intervene' means one lot of letters goes inside another (intervene can mean to enter into).
'ken' placed around 'itch' is 'KITCHEN'.
(Other definitions for kitchen that I've seen before include "where food is a concern" , "Room - thicken (anag)" , "Cooking area" , "In workplace" , "Place to prepare food" .)