Host's moderately tipsy — we've heard that so many times before! (3,4,3,5)
I believe the answer is:
the same old story
'we've heard that so many times before' is the definition.
(familiar story)
'host's moderately tipsy' is the wordplay.
'tipsy' indicates anagramming the letters.
'hosts'+'moderately'='hostsmoderately'
'hostsmoderately' anagrammed gives 'THE SAME OLD STORY'.
(Other definitions for the same old story that I've seen before include "an often-repeated situation" , "engrossing small child at bedtime" , "like the child's book at bedtime?" , "nothing improving" , "What toddlers love at bedtime" .)