Cinema technique showing Frenchman entering second smallest room (3-2)
I believe the answer is:
slo-mo
'cinema technique' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'frenchman entering second smallest room' is the wordplay.
'frenchman' becomes 'm' (abbreviation for Monsieur).
'entering' is an insertion indicator.
'second' becomes 's' (common abbreviation).
'smallest room' becomes 'loo' (loo is a kind of room. I am not sure about the 'smallest' bit.).
's'+'loo'='sloo'
'm' put into 'sloo' is 'SLO-MO'.
'showing' is the link.
Can you help me to learn more?
(Another definition for slo-mo that I've seen is " Slow motion (colloq.)".)