Maybe write about one letter in three months! (6)
I believe the answer is:
winter
'three months' is the definition.
'maybe write about one letter' is the wordplay.
'maybe' is an anagram indicator.
'about' is an insertion indicator.
'one letter' becomes 'n' ().
'write' with letters rearranged gives 'witer'.
'witer' enclosing 'n' is 'WINTER'.
'in' is the link.
(Other definitions for winter that I've seen before include "'Now is the . . . . . . of our discontent' (Richard III)" , "Coldest season" , "period of freeze?" , "Time for mittens and scarves?" , "Cold season" .)