Opted to build a storage facility (5)
I believe the answer is:
depot
'a storage facility' is the definition.
'opted to build' is the wordplay.
'to build' indicates an anagram.
'opted' anagrammed gives 'DEPOT'.
(Other definitions for depot that I've seen before include "Depository for goods" , "Place where buses and trains are kept" , "Terminus for transport vehicles" , "Storage base" , "Storehouse or warehouse" .)