Small submarine command for a group of creatures (8)
I believe the answer is:
suborder
'a group of creatures' is the definition.
(I've seen this before)
'small submarine command' is the wordplay.
'small submarine' becomes 'sub' (synonyms; 'small' indicates a short form).
'command' becomes 'order' (order is a kind of command).
'sub'+'order'='SUBORDER'
'for' acts as a link.
(Other definitions for suborder that I've seen before include "Taxonomic category above family" , "Botanical group" , "Group of creatures" , "Taxonomic group" , "Group of animals" .)