Room height forcing head down a touch (8)
I believe the answer is:
latitude
'room' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for latitude that I've seen before include "Unrestricted" , "comes by degrees?" , "Freedom from restraint or distance from equator" , "Room to manoeuvre or distance from equator" , "Distance north or south of the equator" .)