Unit on the house becoming loose (3,4)
I believe the answer is:
set free
'loose' is the definition.
(synonyms)
'unit on the house' is the wordplay.
'unit' becomes 'set' (unit can mean a set or group of people).
'on the house' becomes 'free' (something on the house is given away free).
'set'+'free'='SET FREE'
'becoming' acts as a link.
(Other definitions for set free that I've seen before include "Uncaged birds have been" , "Liberate" , "Turn loose" , "Deliver - release" , "Clear" .)