Partner that was large gives warning (7)
I believe the answer is:
example
'warning' is the definition.
(as in making an example of someone)
'partner that was large' is the wordplay.
'partner that was' becomes 'ex' (an ex-partner).
'large' becomes 'ample' (similar in meaning).
'ex'+'ample'='EXAMPLE'
'gives' is the link.
(Other definitions for example that I've seen before include "Instance, specimen" , "Standard" , "Typical specimen" , "warning" , "not the actual version" .)