Capital pick-up truck is a tourist attraction (5,2,6)
I believe the answer is:
tower of london
'a tourist attraction' is the definition.
The definition suggests a singular noun which matches the answer.
'capital pick-up truck' is the wordplay.
I cannot really understand how this works, but
'capital' could be 'london' (capital of the United Kingdom) and 'london' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for tower of london that I've seen before include "Building" , "Home to the UK's Crown jewels" , "C eleven capital fortress" , "Capital's castle" , "Where the Crown Jewels are kept" .)