Bear cubs regularly found in dirty spot (7)
I believe the answer is:
sustain
'bear' is the definition.
(I've seen this before)
'cubs regularly found in dirty spot' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'found in' is an insertion indicator.
'dirty spot' becomes 'stain' (synonyms. I am not sure about the 'dirty' bit.).
The alternate letters of 'cubs' are 'us'.
'us' going into 'stain' is 'SUSTAIN'.
Can you help me to learn more?
(Other definitions for sustain that I've seen before include "Feed, nourish" , "Bear (something's weight)" , "Prolong, support" , "Provide nourishment" , "Give food to" .)