Lead or copper primarily seen in deeper ground (7)
I believe the answer is:
precede
'lead' is the definition.
(synonyms)
'copper primarily seen in deeper ground' is the wordplay.
'primarily' indicates taking the first letters.
'seen in' is an insertion indicator.
'ground' indicates an anagram ('grind' the letters into a new form).
The first letter of 'copper' is 'c'.
'deeper' anagrammed gives 'preede'.
'c' inserted within 'preede' is 'PRECEDE'.
'or' is the link.
(Other definitions for precede that I've seen before include "Having to come in front" , "Go before in time or order" , "Go before (someone)" , "Go ahead of" , "be in the van" .)