Son remains in band (4)
I believe the answer is:
sash
'band' is the definition.
(a band of material)
'son remains' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'remains' becomes 'ash' (remains of a fire).
's'+'ash'='SASH'
'in' is the link.
(Other definitions for sash that I've seen before include "Sliding window frame" , "Band of cloth" , "Type of sliding window" , "Cummerbund" , "type of cord?" .)