Spend hour gripped by very popular show (5,3)
I believe the answer is:
shell out
'spend' is the definition.
(I've seen this before)
'hour gripped by very popular show' is the wordplay.
'hour' becomes 'h' (abbreviation).
'gripped by' is an insertion indicator.
'very popular show' becomes 'sell-out' (a sell-out show is very popular).
'h' placed inside 'sellout' is 'SHELL OUT'.
(Other definitions for shell out that I've seen before include "Hand over money" , "Spend" , "pay" , "slogan for oil nimbies?" , "Come up with ready" .)