Pass recalled after start of Baseball League (4)
I believe the answer is:
bloc
'league' is the definition.
(group of nations)
'pass recalled after start of baseball' is the wordplay.
'pass' becomes 'col' (col is a term for a mountain pass).
'recalled' says the letters should be written in reverse (to recall can mean to bring something back).
'after' means one lot of letters go next to another.
'start of' suggests taking the first letters.
The first letter of 'baseball' is 'b'.
'col' reversed gives 'loc'.
'loc' put after 'b' is 'BLOC'.
(Other definitions for bloc that I've seen before include "Political allies" , "Axis (political)" , "Combination of parties or countries" , "multinational group" , "Allied country group" .)