Nuclease required for maintenance of chromosomal stability. Plays a key role in DNA repair of DNA interstrand cross-links (ICL) by being recruited to sites of DNA damage by monoubiquitinated FANCD2. Specifically involved in repair of ICL-induced DNA breaks by being required for efficient homologous recombination, possibly in the resolution of homologous recombination intermediates. Not involved in DNA double-strand breaks resection. Has both endonuclease activity toward 5'-flaps and 5'-exonuclease activity: may act in concert with the 3'-flap-specific enzymes to unhook the ICL by cleaving the lagging-strand template.