がんとして
gantoshite

Adverb
Expression

1. stubbornly; firmly; determinedly; obstinately; resolutely; adamantly

そのおとこがんとしてそのしょくにしがみつき、決けっして退職たいしょくしようとはしなかった。
sono otokowa gantoshite sono shokuni shigamitsuki kesshite taishoku shiyōtowa shinakatta.
The man held on to his job stubbornly and would not retire.