Put the embassy underground during the lull (12)
I believe the answer is:
intermission
'the lull' is the definition.
(thesaurus)
'put the embassy underground during' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'embassy' could be 'mission' (I've seen this before) and 'mission' is found in the answer.
'during' could be 'in' (e.g. during February means in February) and 'in' is present in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for intermission that I've seen before include "Break; respite" , "Interval" , "Theatre's half-time" , "Pause, break" , "Entr'acte" .)