Clear out housing unit that's cleaner in Barnet (7)
I believe the answer is:
shampoo
'cleaner in barnet' is the definition.
'shampoo' can be an answer for 'cleaner' (shampoo cleans hair). I'm unsure of the 'in barnet' bit.
'clear out housing unit' is the wordplay.
'clear out' becomes 'shoo' (to shoo is to clear out or send away).
'housing' means one lot of letters goes inside another.
'unit' becomes 'amp' (amp is a kind of unit).
'shoo' enclosing 'amp' is 'SHAMPOO'.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for shampoo that I've seen before include "Liquid soap" , "Top cleaning product" , "Soap for washing hair" , "Washing preparation (from Hindi)" , "detergent" .)