Depending on how small the amount is and what tax bracket you're in you might want to be aware of personal savings allowance.
Again, depending on how big the 'small' is it might be more tax efficient to make a pension contribution instead.
Edit. Like DW said though, ISA is your first port of call
Edit2. Re the pension thing, if you want this money you're receiving for retirement it's worth being aware of this.
Whether you’ve saved some extra money over the last year or you’ve just received a bonus, there are many reasons for paying a lump sum into your pension.
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