Opening strike recalled by colleague (7)
I believe the answer is:
Here is my best explanation:
'colleague' is the definition.
(I've seen this before)
'opening strike recalled' is the subsidiary indication.
'opening' becomes 'rent' (rent is a kind of opening**).
'strike' becomes 'rap' (rapping is a kind of striking).
'recalled' says the letters should be written backwards.
'rentrap' in reverse letter order is 'partner'.
'by' is the link.
(Other definitions for partner that I've seen before include "Mate or business associate", "Sidekick", "Colleague, bedfellow", "Comrade", "Collaborator", "Professional colleague", "One sharing home or business", "Associate; mate", "teammate" and "Business associate; one of a couple".)