Temporary office left, using this handle over ditch (10)
I believe the answer is:
portakabin
'temporary office' is the definition.
(type of temporary structure used as office space)
'left using this handle over ditch' is the wordplay.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'using this handle' becomes 'aka' ('also known as' is followed by a name or 'handle').
'over' means one lot of letters go next to another.
'ditch' becomes 'bin' (both can mean to reject or throw away).
'port'+'aka'+'bin'='PORTAKABIN'
(Another definition for portakabin that I've seen is " Temporary building".)