One earl dons heartlessly told to get knotted (4)
I believe the answer is:
tied
'knotted' is the definition.
(similar in meaning)
'one earl dons heartlessly told' is the wordplay.
'one' becomes 'i' (Roman numeral).
'earl' becomes 'e'.
'dons' indicates putting letters inside (don means to wear or put on).
'heartlessly' suggests removing the centre.
'told' with its middle removed is 'td'.
'i'+'e'='ie'
'ie' inserted within 'td' is 'TIED'.
'to get' acts as a link.
(Other definitions for tied that I've seen before include "Linked; restricted" , "Fastened with string" , "With an equal score" , "have equal scores" , "In no-win situation" .)