Seeing there's sun, putting the seedlings in their containers (8)

'seeing' is the definition.
The answer and definition can be both to do with contact as well as being present participle verbs.
Perhaps there's an association between them I don't understand?

'sun putting the seedlings in their containers' is the wordplay.
I cannot quite understand how this works, but
'sun' could be 's' (abbreviation) and 's' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
'in' is within the answer.
This explanation may well be incorrect...

'there's' is the link.

Can you help me to learn more?