Gosh! Pound will get a good picnic accessory (4,3)
I believe the answer is:
cool bag
'picnic accessory' is the definition.
(I've seen this before)
'gosh pound will get a good' is the wordplay.
'gosh' becomes 'coo'.
'pound' becomes 'lb' (abbreviation for the unit of weight).
'will get' is a charade indicator (letters next to each other).
'good' becomes 'g' (abbreviation).
'coo'+'lb'+'a'+'g'='COOL BAG'
(Other definitions for cool bag that I've seen before include "picnic accessory" , "Icebox" , "Insulated container for food and drink from the fridge" .)