Tall building — for a carthorse? (5)
I believe the answer is:
tower
'tall building' is the definition.
(I've seen this before)
'for a carthorse?' is the wordplay.
I cannot quite see how this works, but
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tower that I've seen before include "Minaret, for example" , "See 4 Down" , "Rear" , "Campanile, for example" , "Campanile, spire etc" .)