Main lorry unloaded with cunning (6)
I believe the answer is:
archly
'with cunning' is the definition.
(I've seen this in another clue)
'main lorry unloaded' is the wordplay.
'main' becomes 'arch' (I've seen this before).
'unloaded' means to remove the middle letters (the content of the word is unloaded).
'lorry' with its centre taken out is 'ly'.
'arch'+'ly'='ARCHLY'
(Other definitions for archly that I've seen before include "In a sly way" , "In a sly manner" , "In roguish manner" .)