It might come as a surprise at Christmas to gas fitter shedding tears (4)
I believe the answer is:
gift
'fitter shedding tears' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
'it might come as a surprise at christmas to gas' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
The remaining letters 'gif' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for gift that I've seen before include "Give away" , "Donation" , "Knack" , "bent" , "Endowment" .)