Intently watching, but missing a series (6)
I believe the answer is:
string
'series' is the definition.
(sequence of similar items or events)
'intently watching but missing a' is the wordplay.
'intently watching' becomes 'staring' (to stare at something is to watch it intently).
'but missing' is a deletion indicator.
'staring' with 'a' taken out is 'STRING'.
(Other definitions for string that I've seen before include "How long could a piece of it be?" , "Piece of catgut stretched on violin" , "Violin wire/catgut" , "Length of narrow cord" , "Row" .)