Questioning start of gig, with band assumed sick (8)
I believe the answer is:
grilling
'questioning' is the definition.
(grill can mean to question)
'start of gig with band assumed sick' is the wordplay.
'start of' says to take the initial letters.
'with' means one lot of letters go next to another.
'band' becomes 'ring' (synonyms).
'assumed' indicates putting letters inside (inserted letters are assumed or taken in).
'sick' becomes 'ill' (similar in meaning).
The initial letter of 'gig' is 'g'.
'ring' going around 'ill' is 'rilling'.
'g'+'rilling'='GRILLING'
(Other definitions for grilling that I've seen before include "Severe questioning - in oven?" , "Cooking by direct exposure to radiant heat" .)