Something B & B could be? Welcome after old court? (6)
I believe the answer is:
octave
'something b b could be?' is the definition.
I can't judge whether this definition defines the answer.
'welcome after old court?' is the wordplay.
'welcome' becomes 'ave' ('ave' is a Latin greeting).
'after' says to put letters next to each other.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'court?' becomes 'ct' (abbreviation used in road names).
'o'+'ct'='oct'
'ave' put after 'oct' is 'OCTAVE'.
(Other definitions for octave that I've seen before include "Span of eight notes" , "Interval of 12 semitones" , "Note an eighth above or below another" , "Series of eight notes in music" , "At cove (anag.)" .)