Time may be the main issue (6)
I believe the answer is:
season
'time' is the definition.
(I've seen this before)
'the main issue' is the wordplay.
'the main' becomes 'sea' (the main is an old name for the sea).
'issue' becomes 'son' (issue can mean someone's offspring).
'sea'+'son'='SEASON'
'may be' acts as a link.
(Other definitions for season that I've seen before include "Add condiments to for time of year" , "One of four periods" , "Period of a year" , "Major division of year characterised by weather and growth" , "eg.Summer" .)