Coffee shop closes early with onset of substantial overheads (5)
I believe the answer is:
costs
'overheads' is the definition.
(I've seen this before)
'coffee shop closes early with onset of substantial' is the wordplay.
'coffee shop' becomes 'costa' (UK coffee chain).
'closes early' means to remove the last letter (I've seen 'closing early' mean this).
'with' means one lot of letters go next to another.
'onset of' indicates taking the first letters.
The initial letter of 'substantial' is 's'.
'costa' with its final letter removed is 'cost'.
'cost'+'s'='COSTS'
(Other definitions for costs that I've seen before include "Is priced at" , "Overheads" , "Legal expenses" , "Damages" , "Expenditures, outlays" .)