Husband interrupting walk and train of thought (6)
I believe the answer is:
thread
'train of thought' is the definition.
(as in following the thread)
'husband interrupting walk' is the wordplay.
'husband' becomes 'h'.
'interrupting' indicates putting letters inside.
'walk' becomes 'tread' (treading is a kind of walking).
'h' going within 'tread' is 'THREAD'.
'and' is the link.
(Other definitions for thread that I've seen before include "'Strand of cotton, silk etc (6)'" , "Strand for sewing" , "Line of cotton - plot (of book, film)" , "Subject" , "Filament; connecting link" .)