One short month at the submarine centre (3)
I believe the answer is:
mar
'one short month' is the definition.
(short for March; 'short' asks for an abbreviation)
'at the submarine centre' is the wordplay.
'centre' indicates the answer is hidden within the clue (hidden in the middle of the letters).
'MAR' can be found hidden inside 'at submarine'.
(Other definitions for mar that I've seen before include "Ram into and spoil" , "Disfigure" , "Ruin" , "'Damage, impair (3)'" , "Damage; month (abbr.)" .)