Front-page lead story on county's a drop in the ocean (10)
I believe the answer is:
splashdown
'a drop in the ocean' is the definition.
(I've seen this before)
'front-page lead story on county's' is the wordplay.
'front-page lead story' becomes 'splash'.
'on' says to put letters next to each other.
'county' becomes 'down' (County Down in Northern Ireland).
'splash'+'down'='SPLASHDOWN'
(Other definitions for splashdown that I've seen before include "return of spacecraft" , "Landing of spacecraft on water" , "Spacecraft's landing at sea" , "A drop in the ocean" , "End of mission" .)