Big box of chocolates had everyone showing thankful faces (5)
I believe the answer is:
chest
'big box' is the definition.
'chest' can be an answer for 'box' (I've seen this before). I'm unsure of the 'big' bit.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for chest that I've seen before include "It's enclosed by the ribs" , "Large box; thorax" , "Bra on it" , "Rib area" , "Treasure (or heart) container" .)