Poet king takes in (5)
I believe the answer is:
keats
'poet' is the definition.
(John Keats)
'king takes in' is the wordplay.
'king' becomes 'K' (chess abbreviation).
'takes in' becomes 'eats' ('eat' can be a synonym of 'take in').
'k'+'eats'='KEATS'
(Other definitions for keats that I've seen before include "To a Nightingale poet" , "One of two born together" , "John - - (19)" , "Author of the poem Ode to a Nightingale, d. 1821" , "English poet, 1795-1821" .)