Possible Clues:

• Partly lower trousers? What spectacles!
• Perhaps on after the medical officer that's not yet full
• Semicircular object of prince and senior soldier in the nude?
• Semi-visible natural satellite
• Semicircular object
• This is possibly on part of fingernail
• Henry Furlong travels around the earth with satellite that's not fully illuminated
• Henry Furlong travels around the globe from Crescent
• First or last quarter in the lunar cycle
• First or last quarter ... and, literally, what can be found on either end of 18-, 22-, 38-/40- and 49-Across