Sun and Express may be financially sound (7)
I believe the answer is:
solvent
'be financially sound' is the definition.
(I've seen this before)
'sun and express' is the wordplay.
'sun' becomes 'sol' (I've seen this before).
'and' says to put letters next to each other.
'express' becomes 'vent' (venting is a kind of expressing).
'sol'+'vent'='SOLVENT'
'may' is the link.
(Other definitions for solvent that I've seen before include "Having enough money to meet obligations" , "Capable of paying all debts" , "water, for example?" , "liquid chemical" , "Having means" .)