Imagine having to dine and sit together (7)
I believe the answer is:
suppose
'imagine' is the definition.
(I know that imagine can be written as suppose)
'to dine and sit together' is the wordplay.
'to dine' becomes 'sup' ('sup' can be a synonym of 'dine').
'and' is a charade indicator (letters next to each other).
'sit together' becomes 'pose' (as in sitting for a painter. I am not sure about the 'together' bit.).
'sup'+'pose'='SUPPOSE'
'having' is the link.
Can you help me to learn more?
(Other definitions for suppose that I've seen before include "Reckon, think" , "Judge" , "Hypothesize" , "'Believe, perhaps on uncertain grounds (7)'" , "Guess" .)