你的句子去掉 writing 说成 practise calligraphy 也完全可以，因为 practise calligraphy 本来就含有“写”的意思，不过也不能说 practise writing calligraphy 是非正式用法或不符合英语习惯，其实英语是完全可以说write calligraphy 的。我查了一下COCA（美国当代英语语料库），共查到含774例含calligraphy的例句，其中就有不少write calligraphy的例证：

(1) I can write Arabic calligraphy, and I love it.

(2) Tattooing with a partner on the same body is like trying to write perfect calligraphy in a car that's driving down a rocky road…

(3) I wrote like a child—large, clearly distinguishable letters, no calligraphy. Mahmoud could write calligraphy.

(4) “My father would take sticks and write calligraphy in puddles on the ground,” Cai says.

(5) Ideally a famous person wrote the calligraphy for the seal.

(6) Her Grin Grin (paternal grandmother) involves her in the preparations, writing Chinese calligraphy with real ink for decorations

顺便说一句，英语也可以说 write (sth) in calligraphy（其中的in calligraphy表示“用书法的形式”）。如下面的句子也摘自COCA：

(1)…make place cards by simply folding in half an unlined index card and writing in calligraphy.

(2) She wrote the diary in calligraphy and filled it with photographs, drawings, and maps.

(3) McIntosh typed up the forgery and had a Japanese POW write the order in calligraphy to bolster its verisimilitude.