A ledge for support in climbing, only a dot hole (7)
I believe the answer is:
toehold
'a ledge' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'support in climbing only a dot hole' is the wordplay.
'dot hole' can be anagrammed to 'TOEHOLD'.
However, I'm not sure how this is indicated.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for toehold that I've seen before include "Precarious footing?" , "Position of initial advantage from which further substantial progress might be made" , "Advantageous position" , "Minor position from which further progress may be made" , "Small established position" .)