Item, extremely large, at rear of lorry (7)
I believe the answer is:
article
'item' is the definition.
(I've seen this before)
'extremely large at rear of lorry' is the wordplay.
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'at rear of' says to put letters next to each other (some letters go behind others).
'lorry' becomes 'artic' (articulated lorry is a semi-trailer truck).
'large' with its centre removed is 'le'.
'le' put after 'artic' is 'ARTICLE'.
(Other definitions for article that I've seen before include "to cause amusement, say, to a king" , "account in the Financial Times" , "Division" , "Eg, a, an or the" , "thing required" .)