Closely follow pretence circulating these days (6)
I believe the answer is:
shadow
'closely follow' is the definition.
(I've seen this before)
'pretence circulating these days' is the wordplay.
'pretence' becomes 'show' (show is a kind of pretence).
'circulating' means one lot of letters goes inside another (to circulate is to go round).
'these days' becomes 'AD' (as in Anno Domini, after Christ).
'show' placed around 'ad' is 'SHADOW'.
(Other definitions for shadow that I've seen before include "Ghost" , "Image caused by obscuring of light" , "Follow; partial darkness" , "Follow closely - dark image - opposition" , "Darkness caused by obstruction" .)