Opening welcome present for crossworders (6)
I believe the answer is:
hiatus
'opening' is the definition.
(I've seen this before)
'welcome present for crossworders' is the wordplay.
I cannot really see how this works, but
'welcome' could be 'hi' (both are greetings) and 'hi' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for hiatus that I've seen before include "Disruption" , "chasm" , "A gap or lacuna" , "Interruption in intensity or amount" , "Interval" .)