Signal to start playing card game extremely late (7)
I believe the answer is:
whistle
'signal' is the definition.
(whistle is a kind of signal)
'game extremely late' is the wordplay.
'game' becomes 'whist' (whist is a card game).
'extremely' means to remove the middle letters (only the extremes of the word are used).
'late' with its centre taken out is 'le'.
'whist'+'le'='WHISTLE'
'to start playing card' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for whistle that I've seen before include "Musical with Hayley Mills" , "L.S.White (anag.)" , "Hits Lew to make shrill sound" , "Instrument; suit (slang)" , "Blow through teeth" .)