Figure ending in lorry, number in back (6)
I believe the answer is:
ninety
'figure' is the definition.
(I've seen this before)
'ending in lorry number in back' is the wordplay.
'ending in' suggests the final letters.
'number' becomes 'ten' (ten is a kind of number).
'back' is a reversal indicator.
The final letter of 'lorry' is 'y'.
'y'+'ten'+'in'='ytenin'
'ytenin' backwards is 'NINETY'.
(Other definitions for ninety that I've seen before include "Cardinal" , "Figure in inn, yet, strangely" , "nearly a ton" , "Joe perhaps" , ""Top of the shop" in bingo" .)