Slow tempo involving a shed (4,2)
I believe the answer is:
lean to
'shed' is the definition.
(I've seen this before)
'slow tempo involving a' is the wordplay.
'slow tempo' becomes 'lento' (I've seen this in another clue).
'involving' indicates putting letters inside.
'lento' going around 'a' is 'LEAN-TO'.
(Other definitions for lean to that I've seen before include "Show signs of preferring" , "skillion" , "Shanty" , "type of shed" , "conservatory, maybe" .)