The answer to this depends on lots of things. The starting point is who advised you? Were they a qualified financial advisor and did they work for a firm?
Proper advisors should always check your attitude to risk before giving any financial advice, whether that’s about mortgages, pensions, life insurance, etc. If they have done this and you have invested in something which reflects your attitude to risk you may have to accept the fact you’ve lost money and are not entitled to any compensation.
However if you have been misled in some way, for example your money has been put into a high risk fund when you only authorised a low or medium risk investment, then you may be able to claim compensation from the advisor or the firm they worked for at the time.
Have a look at the Financial Services Compensation Service (FSCS) website who have a lot information about your rights and remedies. The FSCS are a government Ombudsman Service and claims about bad advice or miss-selling can usually be put through them. You can do this yourself or get help from a legal professional.
Some claims cannot be dealt with by the FSCS because its not within their remit. You will always have a right to go through the court system.