In retrospect, Everyman has small problem, that's obvious (7)
I believe the answer is:
evident
'obvious' is the definition.
(similar in meaning)
'in retrospect everyman has small problem' is the wordplay.
'in retrospect' says the letters should be written in reverse.
'everyman has' becomes 'I've' (where the crossword setter is 'Everyman').
'small problem' becomes 'dent' (I can't justify this - if you can you should give a lot more credence to this answer).
'ive' in reverse letter order is 'evi'.
'evi'+'dent'='EVIDENT'
'that's' is the link.
Can you help me to learn more?
(Other definitions for evident that I've seen before include "Quite obvious, easy to see" , "on display" , "Quite obvious, manifest" , "Comprehensible - manifest" , "Incontrovertible" .)