Fit porter, maybe, carrying bishop (4)
I believe the answer is:
able
'fit' is the definition.
('able' can be similar in meaning to 'fit')
'porter maybe carrying bishop' is the wordplay.
'porter maybe' becomes 'ale' (type of alcoholic drink).
'carrying' indicates putting letters inside.
'bishop' becomes 'b' (abbreviation used in chess).
'ale' placed around 'b' is 'ABLE'.
(Other definitions for able that I've seen before include "accomplished" , "Gifted" , "Well-equipped" , "Having the skills and qualifications required" , "Competent as, say, sailor" .)