The most common and most likely answer to this crossword clue is the 4 letter word FIRM
F
I
R
M
Buddy explains!

The straight part
We know that "Solid/company" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case solid/company = firm.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.
What does FIRM mean?
FIRM noun- A business partnership; the name under which it trades.
- A business enterprise, however organized.
- A criminal gang, especially based around football hooliganism.
- To make firm or strong; fix securely.
- To make compact or resistant to pressure; solidify.
- To become firm; stabilise.
- To improve after decline.
- To shorten (of betting odds).
- To select (a higher education institution) as one's preferred choice, so as to enrol automatically if one's grades match the conditional offer.
- Steadfast, secure, solid (in position)
- Fixed (in opinion)
- Durable, rigid (material state)