Banks invest reserves initially in bonds (5)
I believe the answer is:
tiers
'banks' is the definition.
(I've seen this in another clue)
'reserves initially in bonds' is the wordplay.
'initially' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'bonds' becomes 'ties' (I've seen this in another clue).
The initial letter of 'reserves' is 'r'.
'r' put within 'ties' is 'TIERS'.
'invest' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tiers that I've seen before include "Layers or thicknesses" , "drawers?" , "Layers of rites" , "Layers, strata" , "Binders" .)