I had ten before time in charge -- that's foolish (7)
I believe the answer is:
idiotic
'foolish' is the definition.
(thesaurus)
'i had ten before time in charge' is the wordplay.
'i had' becomes 'id' (I'd).
'ten' becomes 'io'.
'before' says to put letters next to each other.
'time' becomes 't'.
'in charge' becomes 'ic'.
'id'+'io'+'t'+'ic'='IDIOTIC'
'that's' is the link.
(Other definitions for idiotic that I've seen before include "Half witted" , "without any point" , "Daft" , "Stupid, foolish" , "Silly" .)