Over a kiss (6)
I believe the answer is:
across
'over' is the definition.
(synonyms)
'a kiss' is the wordplay.
I cannot really understand how this works, but
'a' is within the answer.
The remaining letters 'cross' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for across that I've seen before include "ax" , "First word in any crossword" , "...this is 'Number Ten'" , "what follows one here" , "Facing" .)