Some cellos in G minor - they're behind in the score! (6)
I believe the answer is:
losing
'behind in the score' is the definition.
'losing' can be an answer for 'behind' (I've seen this before). I am not certain of the 'in the score' bit.
'some cellos in g minor' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'LOSING' is hidden within 'cellos in g minor'.
'they're' acts as a link.
Can you help me to learn more?
(Other definitions for losing that I've seen before include "Behind in a competition" , "Opposite of 9" , "Mislaying or ceasing to have" , "being beaten?" , "Misplacing or being defeated" .)