Brunel meets Virginia in pub, but fruitlessly (2,4)
I believe the answer is:
in vain
'fruitlessly' is the definition.
(I've seen this before)
'brunel meets virginia in pub' is the wordplay.
'brunel' becomes 'I' (where the crossword setter is 'Brunel').
'meets' says to put letters next to each other.
'virginia' becomes 'va' (US state abbreviation).
'in' indicates putting letters inside.
'pub' becomes 'inn' (an inn is a type of pub).
'i' after 'va' is 'vai'.
'vai' going inside 'inn' is 'IN VAIN'.
'but' is the link.
(Other definitions for in vain that I've seen before include "Without achieving anything" , "useless" , "Fruitlessly" , "Uselessly, to no avail" , "Uselessly, without result" .)