In a perfect world I trade with empty lorry (7)
I believe the answer is:
ideally
'in a perfect world' is the definition.
(in an ideal world)
'i trade with empty lorry' is the wordplay.
'trade' becomes 'deal' (synonyms).
'with' says to put letters next to each other.
'empty' suggests removing the centre.
'lorry' with its centre taken out is 'ly'.
'i'+'deal'+'ly'='IDEALLY'
(Other definitions for ideally that I've seen before include "in optimal way" , "for preference" , "in theory" , "Lay idle (anag)" , "In the perfect case" .)