Dallying in game with King missing lines (8)
I believe the answer is:
coquetry
'dallying in game' is the definition.
'coquetry' can be an answer for 'dallying' (thesaurus). I'm not certain of the 'in game' bit.
'with king missing lines' is the wordplay.
'with king missing' becomes 'coquet' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lines' becomes 'ry' (abbreviation for railway).
'coquet'+'ry'='COQUETRY'
Can you help me to learn more?
(Other definitions for coquetry that I've seen before include "Flirtation" , "Flirtatiousness" .)