First couple's third son established hotel (4)
I believe the answer is:
seth
'first couple's third son' is the definition.
I can't judge whether this definition defines the answer.
'established hotel' is the wordplay.
'established' becomes 'set' (set can mean established or agreed upon).
'hotel' becomes 'h' (phonetic alphabet).
'set'+'h'='SETH'
Can you help me to learn more?
(Other definitions for seth that I've seen before include "A Starkadder" , "In disguise, the brother of Cain and Abel" , "Early man" , "Adam and Eve's third son" , "Cain and Abel's younger brother" .)