Fierce person finally investing in bank (5)
I believe the answer is:
Here is my best explanation:
'fierce person' is the definition.
'tiger' can be an answer for 'person' (tiger is a kind of person). I also know that 'fierce' relates to this answer.
'finally investing in bank' is the subsidiary indication.
'finally' indicates one should take the final letters.
'in' is an insertion indicator.
'bank' becomes 'tier' (**).
The final letter of 'investing' is 'g'.
'g' inserted inside 'tier' is 'tiger'.
(Other definitions for tiger that I've seen before include "Striped quadruped", "''... ... burning bright, in the forests of the night'' (Blake)", "Large forest cat", "Wild cat", "predator", "- - Woods (golf)", "Predator", "One noted for stripes", "Fierce, determined type" and "Large wildcat poetically burning bright".)