Green’s Dictionary of Slang

(US) to be in love with.

1940		J.H. O’Hara Pal Joey 15: They would say that mouse has got it for Joey but bad.
1964		J. Baldwin Blues for Mister Charlie 93: I never had it for nobody bad as I had it for her.
2001		C. Stella Eddie’s World 169: ‘He’s got it for my sister.’ [...] ‘And she’s got it for me’.