An asset to someone in a jam is appreciated by the best footballers (7,5)
I believe the answer is:
perfect pitch
'an asset to someone in a jam is appreciated by the' is the definition.
I can't judge whether this defines the answer.
'best footballers' is the wordplay.
'best' becomes 'perfect' ('perfect' is associated in meaning with 'best').
'footballers' becomes 'pitch' (I can't explain this - if you can you should believe this answer much more).
'perfect'+'pitch'='PERFECT PITCH'
Can you help me to learn more?
(Other definitions for perfect pitch that I've seen before include "Ability to identify notes" , "Note talent" , "Ability to recognise notes accurately" , "playing conditions are ideal?" , "Ability to recognise musical notes by ear - ideal batting surface?" .)