One elderly relative beginning to emerge, senseless (5)
I believe the answer is:
inane
'senseless' is the definition.
(I've seen this before)
'one elderly relative beginning to emerge' is the wordplay.
'one' becomes 'i' (Roman numeral).
'elderly relative' becomes 'nan' (informal term for grandmother).
'beginning to' says to take the initial letters.
The first letter of 'emerge' is 'e'.
'i'+'nan'+'e'='INANE'
(Other definitions for inane that I've seen before include "Thick" , "Absurd" , "Unintelligent" , "Devoid of intelligence" , "Annie (anag.)" .)