These little mammals are I hesitate to say the pits! (7)
I believe the answer is:
ermines
'these little mammals' is the definition.
(ermines are small mammals)
'i hesitate to say the pits' is the wordplay.
'i hesitate to say' becomes 'er' (expression used when hesitating).
'the pits' becomes 'mines' (I've seen this before).
'er'+'mines'='ERMINES'
'are' is the link.
(Other definitions for ermines that I've seen before include "moths" , "Stoats with white winter coats" .)