Fierce person finally investing in bank (5)
I believe the answer is:
Here is my best explanation:
'fierce person' is the definition.
(I've seen this before)
'finally investing in bank' is the wordplay.
'finally' says to take the final letters.
'in' means one lot of letters goes inside another.
'bank' becomes 'tier' (I've seen this before).
The last letter of 'investing' is 'g'.
'g' put within '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".)