Expressionless, Martin put a deposited plan in (7)
I believe the answer is:
deadpan
'expressionless' is the definition.
(I know that expressionless can be written as deadpan)
'martin put a deposited plan in' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'an' and 'an' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for deadpan that I've seen before include "Poker-faced" , "Showing no expression" , "Lifeless" , "Serious-looking" , "without a flicker" .)