Clarify former patent (7)
I believe the answer is:
explain
'clarify' is the definition.
(I know that clarify is a more specific form of the action explain)
'former patent' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'patent' becomes 'plain' (synonyms).
'ex'+'plain'='EXPLAIN'
(Other definitions for explain that I've seen before include "Show the whys and wherefores" , "Describe" , "Tell us how" , "Make understandable" , "Give reason for" .)