Players from Baltimore and Rhode Island in loose formation (7)
I believe the answer is:
orioles
'players from baltimore' is the definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
'rhode island in loose formation' is the wordplay.
'rhode island' becomes 'RI' (US postal abbreviation).
'in' indicates putting letters inside.
'formation' indicates an anagram.
'loose' with letters rearranged gives 'ooles'.
'ri' placed inside 'ooles' is 'ORIOLES'.
'and' is the link.
Can you help me to learn more?
(Other definitions for orioles that I've seen before include "Birds" , "Colourful singers" , "American songbirds" , "Baltimore baseball team" .)