### Clue: Military unit is one of four in southern front that's shelled (8)
### Answer: SQUADRON 
 ### Explanation: Definition: Military unit
 QUAD(short for "quadruplet", one of four children from the same mother in the same delivery) **contained in**(in) [ S(abbrev. for "southern") + "front" **minus its 1st and last letters**(that's shelled) ].