Erected, taken down and mounted (3,2)
I believe the answer is:
put up
'erected' is the definition.
(I've seen this before)
'taken down and mounted' is the wordplay.
'taken down' becomes 'put' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'mounted' becomes 'up' (I've seen this in other clues).
'put'+'up'='PUT-UP'
(Other definitions for put up that I've seen before include "Such a job is one prearranged dishonestly" , "Build - house" , "unfair sort of job" , "Provide shelter" , "Accommodated" .)