Rock managed in-house (7)
I believe the answer is:
granite
'rock' is the definition.
(type of rock)
'managed in-house' is the wordplay.
'managed' becomes 'ran' (both can mean organised or was in charge of).
'in' means one lot of letters goes inside another.
'house' becomes 'gite' (I can't justify this - if you can you should give a lot more credence to this answer).
'ran' inserted inside 'gite' is 'GRANITE'.
Can you help me to learn more?
(Other definitions for granite that I've seen before include "A very hard rock from Tangier" , "Very hard type of rock" , "determination" , "Coarse-grained igneous rock" , "Hard igneous rock" .)