That chap's tense about international criminal operation (5)
I believe the answer is:
heist
'criminal operation' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'that chap's tense about international' is the wordplay.
'that chap's' becomes 'hes'.
'tense' becomes 't' (abbreviation used in many dictionaries).
'about' indicates putting letters inside.
'international' becomes 'i' (abbreviation eg in IMF).
'hes'+'t'='hest'
'hest' placed around 'i' is 'HEIST'.
Can you help me to learn more?
(Other definitions for heist that I've seen before include "Bank robbery" , "criminal activity" , "crime?" , "Armed robbery" , "Armed hold-up (sl.)" .)