Fancied precious metal parts one dug up (8)
I believe the answer is:
imagined
'fancied' is the definition.
(I've seen this before)
'precious metal parts one dug up' is the wordplay.
'precious metal' becomes 'Ag' (Ag is the chemical symbol for silver).
'parts' is an insertion indicator (in the sense of cuts or separates).
'one' becomes 'i' (Roman numeral).
'dug up' becomes 'mined' (I've seen this in another clue).
'i'+'mined'='imined'
'ag' inserted inside 'imined' is 'IMAGINED'.
(Other definitions for imagined that I've seen before include "Not based on fact, dubious" , "Supposed" , "Conjured up in the mind" , "Fancied" , "Envisaged" .)