Meaning:
“直” here means “continuously,” “呼” means “to call,” and “内行” refers to “an expert.” The saying, which literally means “someone being continuously called an expert, usually by another expert,” became popular last year after a short video went viral. In that video, a young man at a buffet dinner walks directly to the sector of seafood and piles a lot of shrimp, fish and scallops on his plate, and therefore the restaurant owner calls him “an expert,” because the seafood is the most expensive food at a buffet. Netizens always use the saying jokingly to praise others.
Example:
A: 你觉得我的新家好看吗？是我自己设计的。
Nǐ juéde wǒ de xīnjiā hǎokàn ma？Shì wǒ zìjǐ shèjì de。
Is my new apartment nice? I designed the interior myself.
B: 太好看了，职业设计师都要直呼内行。
Tài hǎokàn le，zhíyè shèjìshī dōu yào zhíhū nèiháng。
Very nice. A professional interior designer will call you an expert.