Increase got by former partner -- harshly criticised, we hear (6)
I believe the answer is:
expand
'increase' is the definition.
(expanding is a kind of increasing)
'by former partner harshly criticised we hear' is the wordplay.
'by' means one lot of letters go next to another.
'former partner' becomes 'ex' (an ex-partner).
'harshly criticised' becomes 'panned' (pan can mean to criticise severely).
'we hear' shows a homophone (sound like).
'panned' sounds like 'pand'.
'ex' put next to 'pand' is 'EXPAND'.
'got' is the link.
(Other definitions for expand that I've seen before include "Broaden" , "Make more extensive" , "Increase in volume" , "inflation" , "put on weight?" .)