'Tabloid Kelvin' is done for (4)
'done for' is the definition.
('sunk' can be a synonym of 'done for')
'tabloid kelvin' is the wordplay.
'tabloid' becomes 'sun' (The Sun, UK newspaper).
'kelvin' becomes 'k' ('K' can be a synonym of 'kelvin').
'is' acts as a link.
(Other definitions for sunk that I've seen before include "Sent to bed", "Doomed - bored", "(Has) disappeared beneath the waves", "Submerged", "suffered decline".)