Magnificent valley moguls regularly visited (8)
I believe the answer is:
gorgeous
'magnificent' is the definition.
(I've seen this before)
'valley moguls regularly visited' is the wordplay.
'valley' becomes 'gorge' (gorge is a kind of valley).
'regularly visited' means one should take alternating letters (letters are taken at regular intervals).
The alternate letters of 'moguls' are 'ous'.
'gorge'+'ous'='GORGEOUS'
(Other definitions for gorgeous that I've seen before include "Strikingly beautiful" , "Magnificently beautiful" , "Stunning" , "Extremely beautiful" , "Wonderful to taste or look at" .)