Monument shows oddly droll fellows (6)
I believe the answer is:
dolmen
'monument' is the definition.
(dolmen is a kind of monument)
'oddly droll fellows' is the wordplay.
'oddly' indicates alternate letters.
'fellows' becomes 'men' (I've seen this before).
The alternate letters of 'droll' are 'dol'.
'dol'+'men'='DOLMEN'
'shows' acts as a link.
(Other definitions for dolmen that I've seen before include "ancient monument" , "Ancient tomb for old men" , "Prehistoric megalithic tomb" , "Type of megalithic tomb" .)