President once was able to buy off a Fed (4)
I believe the answer is:
ford
'president once' is the definition.
(Gerald Ford)
'able to buy off a fed' is the wordplay.
I cannot really see how this works, but
'to' could be 'for' and 'for' is found in the answer.
A single letter 'd' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'was' acts as a link.
(Other definitions for ford that I've seen before include "Harrison - - (film actor)" , "White paint for the face" , "Car firm" , "US President - river crossing" , "Shallow crossing point in river" .)