Group of soldiers weep over sad tune (7)
I believe the answer is:
century
'group of soldiers' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'weep over sad tune' is the wordplay.
'weep' becomes 'cry' ('cry' can be a synonym of 'weep').
'over' indicates putting letters inside.
'sad' is an anagram indicator.
'tune' anagrammed gives 'entu'.
'cry' placed around 'entu' is 'CENTURY'.
Can you help me to learn more?
(Other definitions for century that I've seen before include "Period of time" , "lot of time" , "One hundred years" , "100 years" , "Group of a hundred" .)