Comedy modelled on international soldiers (6)
I believe the answer is:
satire
'comedy' is the definition.
(thesaurus)
'modelled on international soldiers' is the wordplay.
'modelled' becomes 'sat' ('sit' can be a synonym of 'model').
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'international' becomes 'i' (abbreviation eg in IMF).
'soldiers' becomes 're' (Royal Engineers).
'sat'+'i'+'re'='SATIRE'
(Other definitions for satire that I've seen before include "Irony or sarcasm in speech or writing" , "Humorous criticism of folly or vice" , "burlesque" , "Humouous piece which ricicules" , "Parody, spoof" .)