A new shirt PC ordered — I’d retain his helmet? (9)
I believe the answer is:
Here is my best explanation:
'i'd retain his helmet?' is the definition.
I know that 'helmet' relates to this answer.
'a new shirt pc ordered' is the subsidiary indication.
'new' becomes 'n'.
'ordered' is an anagram indicator.
'anshirtpc' is an anagram of 'chinstrap'.
(Other definitions for chinstrap that I've seen before include "fastener", "securing device", "bit", "This secures cover for head", "Retainer", "Band", "Bit of helmet", "Thong to hold on helmet" and "hat".)