Runner on form perhaps marks female group (5)
I believe the answer is:
harem
'female group' is the definition.
'runner on form perhaps marks' is the wordplay.
'runner on form perhaps' becomes 'hare' (hare can mean a fast runner).
'marks' becomes 'm' (former German currency).
'hare'+'m'='HAREM'
(Other definitions for harem that I've seen before include "Home to concubines" , "Living quarters of wives in a Muslim household" , "Separate women's quarters" , "A lot of females" , "Quarters occupied by women by Muslim household" .)