Poet providing king with grub (5)
I believe the answer is:
keats
'poet' is the definition.
(John Keats)
'king with grub' is the wordplay.
'king' becomes 'K' (abbreviation for king in chess).
'with' means one lot of letters go next to another.
'grub' becomes 'eats' (synonyms).
'k'+'eats'='KEATS'
'providing' acts as a link.
(Other definitions for keats that I've seen before include "Author of the poem Ode to a Nightingale, d. 1821" , "Author of Endymion and Ode to a Nightingale" , "Ode to Autumn poet" , "English odist" , "One of two born together" .)