Extremely popular digging tools (2,6)
I believe the answer is:
in spades
'extremely' is the definition.
(I've seen this before)
'popular digging tools' is the wordplay.
'popular' becomes 'in'.
'digging tools' becomes 'spades'.
'in'+'spades'='IN SPADES'
(Other definitions for in spades that I've seen before include "Woman's garment" , "to a great extent" , "Not half!" , "to a large degree" , "Emphatically" .)