Dull as some peculiar ideas (4)
I believe the answer is:
arid
'dull' is the definition.
(I've seen this in another clue)
'some peculiar ideas' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ARID' is hidden within 'peculiar ideas'.
'as' is the link.
(Other definitions for arid that I've seen before include "Dry raid" , "Very dry; uninteresting" , "Dry and unfertile" , "Dry and infertile" , "Very dry, having little rain" .)