Tall; expensive (4)
I believe the answer is:
high
This clue is a double definition.
'tall' is the first definition.
(similar in meaning)
'expensive' is the second definition.
(I've seen this in another clue)
(Other definitions for high that I've seen before include "Drunk; anticyclone" , "Eminent; lofty" , "Tall - loud - under the influence of drugs" , "Far above ground level" , "In slang, under the influence of drugs" .)