The most common and most likely answer to this crossword clue is the 15 letter word PRESTIDIGITATOR
I've seen this crossword clue in The Guardian
P
R
E
S
T
I
D
I
G
I
T
A
T
O
R
More clues leading to the result PRESTIDIGITATOR
- “God is tripartite” corrected conjurer
- Figure captivated by performing artist — rope tricks are his speciality
- Tricky performer‘s piano support that is enjoyed by me before a Glastonbury feature
- He conjures a report up about Stig concealing identity with personal magnetism
- Magician gets religious man to move one toe with a twig? Ordinary ruse for starters
- Peace and quiet beforehand... I enjoy it
Buddy explains!
The straight part
We know that "tricks are his speciality" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tricks are his speciality = prestidigitator.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.