Small edible fish (5)
(Other definitions for sardines that I've seen before include "Young pilchards" , "Cumulative hiding game" , "Children's game - fish" , "Small fish, usually canned" , "Squash-together party game" .)
'small edible fish' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sprat that I've seen before include "Traps (anag.)" , "Couple sharing meat" , "one on a fat-free diet" , "little fish" , "Tiny fish" .)