What's been leaked? Consult attendant (7)
I believe the answer is:
seepage
'what's been leaked?' is the definition.
(something that has seeped out)
'consult attendant' is the wordplay.
'consult' becomes 'see'.
'attendant' becomes 'page' (page is a kind of attendant).
'see'+'page'='SEEPAGE'
(Other definitions for seepage that I've seen before include "Discharge" , "Ooze" , "Slow leakage" , "Leaking liquid" , "Slow leaking flow" .)