A silently constructed but conspicuously (9)
I believe the answer is:
saliently
'conspicuously' is the definition.
(thesaurus)
'a silently constructed' is the wordplay.
'constructed' is an anagram indicator.
'a'+'silently'='asilently'
'asilently' anagrammed gives 'SALIENTLY'.
'but' is the link.
(Other definitions for saliently that I've seen before include "Most importantly" , "in striking fashion" .)