Wrote letters in a tall building (5)
I believe the answer is:
tower
'a tall building' is the definition.
(I've seen this in another clue)
'wrote letters' is the wordplay.
'letters' indicates an anagram.
'wrote' is an anagram of 'TOWER'.
'in' is the link.
(Other definitions for tower that I've seen before include "Rear" , "Monument" , "Drawer" , "See 4 Down" , "Tall structure" .)