DeiSaku is the term used to refer to the romantic relationship between Deidara and Haruno Sakura
Kazekage Rescue Arc
When Deidara lures Naruto out of the cave to fight with him, Sakura stays with Chiyo inside to battle Sasori.
Although they didn't speak with each other, it is revealed that Sakura acknowledged Deidara as someone strong enough to take down the Kazekage. Deidara openly asked Naruto if he really believed that she and Chiyo could take down his partner, refering to Sakura as "little girl".
None. This is a Crack Pairing.
Among the fans
DeiSaku has a fair amount of fans in the fandom and is arguably one of Deidara's most popular heterosexual pairings. It is likely that people ship it because of their personalities and fighting styles, which seem to match to some considering that Sakura uses her strength to destroy things in a blink of an eye where Deidara might consider as art.