Calendar gals stripped (one not in the buff) (7)
I believe the answer is:
almanac
'calendar' is the definition.
(I've seen this before)
'gals stripped one not in the buff' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'an' (an apple is one apple) and 'an' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for almanac that I've seen before include "Yearly publication with calendar etc" , "Kind of year-book like Old Moore's" , "Annual publication containing information in a particular field" , "Year book with astronomical events, tides etc" , "Annual reference book" .)