One slipping along to put a gloss finish on the shelf (6)
I believe the answer is:
sledge
'one slipping along to' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'a gloss finish on the shelf' is the wordplay.
'finish' indicates one should take the final letters.
'on' is a charade indicator (letters next to each other).
'the shelf' becomes 'ledge' (synonyms).
The last letter of 'gloss' is 's'.
's'+'ledge'='SLEDGE'
'put' is the link.
Can you help me to learn more?
(Other definitions for sledge that I've seen before include "Vehicle for travelling over snow" , "Snow vehicle or heavy hammer" , "In the field, abuse" , "heavy tool" , "Vehicle on runners, for snow and ice" .)