Assemble on south courtyard right in front of a military unit (8)
I believe the answer is:
squadron
'military unit' is the definition.
(I know that squadron is a type of air unit)
'assemble on south courtyard right in' is the wordplay.
'assemble' indicates an anagram.
'south' becomes 'S' (abbreviation).
'courtyard' becomes 'quad' (short for quadrangle).
'right' becomes 'r' (common abbreviation).
'in' is an insertion indicator.
'quad'+'r'='quadr'
'on'+'s'='ons'
'ons' with letters rearranged gives 'son'.
'son' going around 'quadr' is 'SQUADRON'.
'front of a' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for squadron that I've seen before include "Air force grouping" , "Unit of warships, planes" , "Air or naval unit" , "Military unit" , "Navy, army or air force unit" .)