One who gives out marks missing in term-time mix-up (7)
I believe the answer is:
emitter
'one who gives out' is the definition.
(someone or something who emits)
'marks missing in term-time mix-up' is the wordplay.
'marks' becomes 'm' (former German currency).
'missing in' suggests deleting specific letters.
'mix-up' indicates anagramming the letters.
'term'+'time'='termtime'
'termtime' with 'm' removed is 'tertime'.
'tertime' with letters rearranged gives 'EMITTER'.
(Other definitions for emitter that I've seen before include "Something giving out (eg, a radio signal)" , "Region in a transistor" , "One part of a transistor" , "electronic component" .)