Mischievous sprite (3)
'mischievous sprite' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for elf that I've seen before include "Fairy, pixie" , "Robin Goodfellow?" , "He causes mischief" , "Imp-like being" , "Pixie (able to cobble?)" .)
(Other definitions for puck that I've seen before include "Mischievous spirit" , "Disc used in ice-hockey" , "One of 5 [FAIRIES]" , "Mischievous sprite or disc for ice hockey" , "something a bit like a mouse" .)
'mischievous sprite' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for gremlin that I've seen before include "Mischievous sprite" , "Troublemaking goblin" , "Cause of mechanical failure?" , "Fault-inducing sprite" , "Imp causing mechanical problems?" .)