Force Merlin to sort out unexplained fault (7)
I believe the answer is:
gremlin
'unexplained fault' is the definition.
'gremlin' can be an answer for 'fault' (I have seen 'Mechanical fault ' mean 'gremlin' so perhaps 'fault' could also mean 'gremlin'). I am not certain of the 'unexplained' bit.
'force merlin to sort' is the wordplay.
'force' becomes 'g' (short for gravity).
'to sort' indicates anagramming the letters.
'merlin' anagrammed gives 'remlin'.
'g'+'remlin'='GREMLIN'
'out' acts as a link.
Can you help me to learn more?
(Other definitions for gremlin that I've seen before include "Trouble-making imp" , "Mischievous machine saboteur" , "Mischievous goblin" , "mischievous type" , "Fault-causing sprite" .)