New financial institution losing pounds over a quarter (6)
I believe the answer is:
autumn
'a quarter' is the definition.
(quarter of the year)
'new financial institution losing pounds over' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'financial institution' becomes 'mutual' (mutual fund).
'losing' is a deletion indicator.
'pounds' becomes 'L' (abbreviation e.g. Lsd - pounds, shillings, pence).
'over' shows that the letters should be reversed in order.
'mutual' with 'l' taken away is 'mutua'.
'n'+'mutua'='nmutua'
'nmutua' written backwards gives 'AUTUMN'.
(Other definitions for autumn that I've seen before include "Fall for Mrs Obama" , "Harvest season" , "Fall in North America" , "'O wild West Wind, thou breath of . . . . . . 's being' (Shelley)" , "Browning happened then" .)