What does 可是 mean?

Question

A daughter to her police father,

"How did you find me?" “你怎么找到我的？”

"I'm a detective." “我可是个警探。”

可是 means

but however yet

But it doesn't make sense here.

Answer 1

Here 可是 is two words 可 + 是 and not one word: 可是. Here 可 + 是 is an adverbial phrase that it used to emphasize something. Take a look at Pleco C-E's definition:

ADVERB
[for emphasis]

这鱼可是新鲜的。
Zhè yú kě shì xīnxiān de.
The fish is really fresh.

说话可是要算数的。
Shuōhuà kě shì yào suànshù de.
You can never go back on your word.

Answer 2

This 可 is to emphasize the statement. In English you would just pronounce "is" or "am" emphatically.

“我可是个警探。”
I am a detective.

这可是最大的一块蛋糕。
This is the biggest piece of cake.

我可是我们班最高的。
I am the tallest in our class.