Finally ask: Now who, perhaps, has the expertise? (4-3)
I believe the answer is:
know-how
'the expertise?' is the definition.
(I've seen this before)
'finally ask now who perhaps' is the wordplay.
'finally' suggests the final letters.
'perhaps' indicates anagramming the letters.
The final letter of 'ask' is 'k'.
'who' anagrammed gives 'how'.
'k'+'now'+'how'='KNOW-HOW'
'has' acts as a link.
(Other definitions for know-how that I've seen before include "Ingenuity - aptitude - skill" , "Ingenuity - experience" , "Ingenuity - aptitude - knack" , "Practical knowledge or skill" , "Specialised skill" .)