Homosalate is not an ideal UV filter on its own, due to its low-level protection and is not photostable (loses 10% of its SPF protection in 45 minutes), so it must still be mixed with other sunscreens to provide adequate protection. Its key advantage is that it is a liquid and is excellent for dissolving other difficult-to-solubilize powder sunscreen agents.

See also:
UVA
UVB

Ref:
Couteau, C., et al. "Study of the efficacy of 18 sun filters authorized in European Union tested in vitro." Die Pharmazie-An International Journal of Pharmaceutical Sciences 62.6 (2007): 449-452.
Couteau, Céline, et al. "Study of the photostability of 18 sunscreens in creams by measuring the SPF in vitro." Journal of pharmaceutical and biomedical analysis 44.1 (2007): 270-273.