Happen to enter bloc, curious (5)
I believe the answer is:
occur
'happen' is the definition.
(I know that happen can be written as occur)
'enter bloc curious' is the wordplay.
'enter' says the answer is hidden in the clue (I've seen 'entering' mean this).
'OCCUR' is hidden within 'bloc curious'.
'to' is the link.
(Other definitions for occur that I've seen before include "Befall" , "Spring to mind" , "Happen, transpire" , "exist" , "appear" .)